From the humble beginnings of Eliot Coleman's New Organic Grower comes the World's Resource for Garden Soil Block Makers as seen on Johnny's Seeds.
Wednesday, January 6, 2016
Starting a Commercial Nursery Business Using Soil Blocks and Soil Block Makers
Introduction to the Soil Block Nursery Transition...
Here is a series of questions and answers from a recent consulting gig for Penobscot Potting Shed, Maine. Many of you are coming here in search of "How-To" information on starting or converting your nursery, greenhouse, or farm into a soil block seedling, transplant, and propagation business and commercial enterprise. Read here how one Maine farmer turned a vegetable seedling start-up business into a full blown soil block nursery business using these strategies. Enjoy!
But first, a little about them. We are a small family run organic nursery business. There are three of us, myself (Andy), Tania and Tobin (4 years old). Tania and I met in South Korea teaching English and when Tobin was 6 months old we decided it was time to move along and settle in Maine to have a small farm. We quickly decided to change our plan a little and focus on being an organic propagation nursery. We got certified organic last year, our first year, and sold a few thousand plants. But mostly worked on infrastructure. Everything we grow is organic and we are focusing on heirloom and open-pollinated vegetables, flowers and herbs and also native plants grown from seed. Last year we were accepted into the MOFGA Journey Persons program. It is a two year program. A part of that program is the education/mentor program for which MOFGA provides a small stipend. They insisted our first year be with a local farmer, but agreed that this year we could broaden our range since nobody locally was doing quite what we are trying to do. So we contacted you.
A little about our nursery. We live on just under 3 acres. That is part of what directed us to being a propagation nursery instead of a farm- lack of land base. We currently have two 19x48 foot single layer poly greenhouses with benches we grow plants out in. One is finished and up now (under heaps of snow!) with wire benches we salvaged from an older nursery down the road. The other has its frame up but we are awaiting spring to put plastic on and will probably build wooden benches. We also have one 21x28 double layer inflated greenhouse in our driveway. This will be a heated house (propane heater still to be installed this winter but onsite) that we will start plants in and then hope to transition to a growing/retail space come spring/summer. We begin seeds indoors on "metro-shelves" and move them out to the heated house. We also use the metro-shelves as display carts that we supply to our wholesale customers at natural food stores, etc. We also start native seeds from seed in potting blocks and then plant them out into the field to grow our for the year and dig them up the following spring for potting up into Cowpots.
A little about our goals as a business. Currently Andy works off farm full time. The end goal is to support our family with our nursery.
Most of our plants start life in a germination block or 1.5" block and then are typically potted up into a larger block. We then pot up a lot of those plants into Cowpots. Last year we experimented a little with selling soil blocks at our local Farmers' Market. We had kale and flowering Johnny Jump-Ups to introduce customers to the idea of soil blocks. We had a lot of education to do but encouraged customers to 'bring their own container'. At market they selected the plants from the 1020 tray and put them into 'beer boxes' (the shallow boxes that canned drinks come to grocery stores in) to take away if they didn't have their own. As far as experiments go it was a huge success. A lot of the local farmers use soil blocks themselves, but they had never thought of offering them for sale to customers. We had great feedback about the soil blocks and a lot of repeat customers and a lot of questions about what we would be offering in the future...
We would like to sell more soil blocks- they are obviously the best choice for the plant and we use them in the beginning stages of everything we sow. Building various sized wood seedling trays branded with our logo is a great idea! And a great way to reduce our use of plastic. We have spoken to our local sawyer and he is able to supply cedar or other species of wood down to a 1/4 inch thick. We would love to learn more about your building process and are brainstorming jigs, etc. now. We were hoping to develop a cut list to supply several sizes of trays and order them in the widths that we need and whatever lengths the sawyer has them in. Then transport them home, cut them to length and assemble. We would love to learn more about your building process, screws and drill vs staples and air gun, jigs, etc.
The Consulting of a Soil Block Business...
-Growing: do you prefer wire benches or wood in the greenhouse? Do you use flats on the benches or do you just put the soil blocks straight on wood slats or wire?
I prefer wire: Called quail fence where I'm from it is a 1/4" by 1/2" heavy duty galvanized wire sold int 24" width up to hundreds of feet. All you do is roll it out over the greenhouse bench frames, which, by the way, is made out of ALL galvanized pipe same as the greenhouse. The all galvanized set up is 24" by the length of the greenhouse with cross braces every 2'. Wood can be used for benching, but guess what? Rot sets in and you'll be swamped with the redo when sales are busting out. Do it all galvanized to start if you can. Now, l love starting on pure wire, but with a plastic flat, like a 1020, or a 17" x 17" mesh bottom trays. This is because I use heat mats, and a LOT of heat mats to start seedlings. My suggestion is heat mats, but with the foil bubble foil radiant barrier underneath them. Heat mats are on side and you just keep the trays sliding down off the mat like a production line.
-Wood trays: Do you use wood flats from the beginning or only for retailing? Is it possible to bottom water with wood flats? We hear they help retain soil moisture but what about damping off? What happens to the roots on a solid surface? Do any species of wood retard growth?
Wood trays ONLY for retail, use wire and mesh flats for greenhouse work, or nothing at all. No, rots, warping, and leaks makes wood unsuitable for Bottom Watering. Bottom watering is a watering system, a business is going to go into like a hydroponic garden: LEVEL MONO TRAYS with ebb and flow type timing. It is a serious investment of time and expertise. It is good, no doubt, no worries of damping off, which, by the way is solved by 4 things: 1: Proper seed germination heat for rapid growth. 2. Light, and lots of it! 3. Fans, Fans, and more Fans! 4. Greenhouse CROSS ventilation.
Roots on a solid surface can end up mingling with others causing a slowdown at transplant time when one wants to transplant due to root tearing. Always use air gaps and proper spacing on solid surfaces. No species of wood in my experience retards growth when used as a bench. But, of course, NEVER EVER in a block mix.
-Watering: Can you bottom water in wood flats? Do you bottom water?
NO. I DO, I DID, I DON'T Anymore. I Did it all. I LOVE automatic overhead and under wire bench MISTING, FOGGING. The oxygen content makes plants EXPLODE into growth. If you are present with your plants use Fogging on timers. We can cover this later.
- Soil mixing: We currently blend our own mix (based on Eliot Coleman's recipe) and are experimenting with an OMRI approved pre-blended mix from Vermont Compost Company this year. What do you do for a soil mix? Different mixes for germination blocks and larger blocks? Do you screen the soil for germination blocks and down to what size? Andy is particularly interested in how many blocks you can process in an hour for the different sized blockers. Do you mix soil in a cement mixer? Is there any special equipment you use or can recommend? We are trying to decrease our use of peat by using composted aged bark instead that is available locally already mixed with loam (soil) and compost.
Now here we go with the absolute SOUL of the business: SOIL! Ahhhh, how it will make or break you in so many ways, we must cover this perhaps on the phone....But, I'll give it a shot! First off, after your infrastructure is built, your soil is the one thing you have to keep making or buying, right? Expensive soil reduces profits, but cheap soil loses customers. Its an art how to do this to be profitable and sustainable.
I do not know how well Vermont Compost is with their pre-blends. But, I ALWAYS did EXTENSIVE trial runs before turning over soil blocks to customers. So, How is it??? I made my own Eliot recipe until I found a local source very, very similar. That was lucky! Maybe you'll get lucky too! But, remember: The soil block has to have enough compost or vermi-compost in it to keep a lazy customer's soil block seedlings fertilized until they plant it. So, treat your trial runs like the grower and the negligent customer. (YOU WILL THANK ME FOR THIS PRICELESS ADVICE!!!! Hee hee hee, think how they'll be running back to as a repeat customer when you've made them look so good, versus a dead plant because of a dry, weak soil block.)
Careful with compost, it could be drying, and drying compost in the hands of a customer is dangerous. I advise you to find someone to make it for you if Vermont is not up to standards. I always use coco coir and peat moss (skip the debate for now, going too green, too early, could be risky) and worm castings, perlite, and the Eliot base fertilizers. The germination blocks, 3/4" soil blocks, will use a germ mix and be sifted to a 1/4", which is basically without the nitrogen fertilizers, so one size could fit all, but I had 3 mixes: 1 germ (3/4"), 1 soil block (1.5,2,3"), and the BIG BUDGET BLOCK MIX (4") as the tomato, pepper, eggplant, and even whole herbs, lettuce heads and celery, etc., could be soil in a 4 inch soil block, but wow! the amount of soil is a money pit! Use budget ingredients like larger bulkier items that don't need to be sifted. They key here is: The smaller the soil block, the better the long-term nutrition and water absorbing mediums like coco coir and worm castings should be, because the roots can be nourished through that block. The 4" block is providing stability more root growth and top leafy growth. One mix can do it all, but then, it will have to be sifted to 1/4". I think that would be fine, especially if we are going to get you scalable. You must keep investigating local sources of ingredients, mixers, makers, and work on bulk buying deals. Invest heavily upfront when you find the soil block mix that works for you. This is number crunching time here!
Well, I can do 1,000 per hour of a 2" soil block, but 2 people can do 2,000. Think production line: Wet the soil, feed the soil block maker, moving the trays down the line and/or ready to seed. System, system, system, and staff, staff, staff. I was a one man show, but I did have periodic help: Training someone and then losing them next week loses time in the long run.
I can say that each soil blocker on my website has that technical detail. Those rates are normally for one experienced blocker or 2 regular workers.
Yes, use a cement mixer for both the mixing of the soil and wetting the block mix. Shop Northern Tool out of Minnesota for their LARGEST electric mixer, I forgot what mine was in terms of cubic foot. Don't worry about the poor remarks and reviews. This tool has gotten better as of late, and it is only going to be used for potting soil, NOT cement, so it will work like a summer breeze!
Please stay away from composted bark, it will set you back weeks and cause major problems. The peat issue is, at this point, still a debate. Eliot Coleman believes in it, shouldn't we? It is mostly hype right now, and the ONE BEST WAY to feel good about using peat, which is going to be vital to your upstart business to gain on margins is BUY PEAT MOSS FROM COMPANIES WITH THE CANADIAN SPHAGNUM PEAT MOSS ASSOCIATION. You'll be safe, the environment will be safe, and you will have the BEST blocking mix.
Cocopeat, Coco Pith, Coco Fiber, Coconut growing mediums are an extremely variable product with numerous manufacturing processes leaving many end results in quality, consistency, textures, ph levels, and potential salts. Thoroughly investigate each and every Coco Peat dealer or manufacturer to uncover their process and credibility through other growers, and then get samples and grow plants from seeds before investing in their bulk products. Cheaper is not better, go with reputation and other growers’ results and your own test runs before using.
Ideally, here, if this business is to work on profit, you must make your own blocking mix and even your own compost or worm castings in the future. This insures a solid branded one-of-kind soil block transplant that can not be duplicated by competitors. Just by seeking me out, you're already miles ahead of any competition in the future. So, I will say this: Perfect your compost making techniques so that when the compost is finished, IN AND OF ITSELF, ALL BY ITSELF, it will be your blocking mix! There is time and strategy to go into this method, so practice NOW. So, in 2-3 years, you have an endless supply of blocking mix, and you will be free of all inputs to your farm.
This "compost block mix" is a technique me and a few other growers have worked with and the results are in. It works! We'll talk about the procedure later. Let me know you're interested by saying show me the way to "compost block mix".
-Plants: how to plant 'transplant sensitive plants'- e.g. cilantro or dill- how deep so they don't get leggy, do you cover these seeds- would it be better to multi-plant a block with the intention of them putting into a container as the final product? Selling the plants younger? Which kinds of seedlings lend themselves to being planted deeper in the final planting e.g. kale, beets, chard, tomatoes, ground cherries etc.?
OK, I love your spirit here....However, there is nothing sensitive about any plant when one uses the soil block system and provides air gaps and air-root pruning techniques, right? Legginess is ONLY due to low lighting....YOU BETTER START ALL YOUR PLANTS IN A GREENHOUSE and start them ONLY 10 days before there will be 10 hours of daylight: Consult the farmers almanac or Eliot Coleman's books! Trust me, you'll catch up to anybody anywhere when you follow this timing (and the moon cycles, too, which we can elaborate on later).
MULTIPLANTS are for the produce market gardener, NOT nursery sales. Why? They consume too much water and feed, and look to messy and customers will not get the spacing right. The market is not ready for it, please don't do it.
I offered up different stages of growth for more or less money, it is up to you, but the point is, you can't charge the same for different aged plants, because they'll all buy up the BIG ONES and leave the small ones for next week. (And, next week means taking plants home for the night after a day at the market, or wholesale delivery, or stocking retail outlets.) I would aim for one size, one price, that is what I've learned. Make 'em bigger, make 'em better, and sell 'em for more, keep the lil' ones at home until they grow up. People like lots of green!
You can almost plant any plant deeper at final planting, and that should be taught to your customer. Except for what I call the "heart plants", the ones that have a edible heart: lettuce, celery, radicchio, spinach, you see?
-Selling: What size blocks do you sell and what do you charge for wholesale/retail for each block size? Do you price by the flat? Discounts? We have several wholesale accounts that we sell to, direct retail off farm and at a farmers market.
The question is: What will the market bear? Because too cheap, and you're out plants and not much return capital, just the opposite for too expensive. What is profitable? What takes the least amount of time for the most margin? I will only throw out some ideas, but your area is specific and your customers YOU MUST KNOW. Surveys are great, remember these words! For Retail Try 2 bucks a 2" block, 3 bucks a 3" block, 6-8 bucks for a 4" soil block. (Because, if they're rooted and stable, they don't require any special handling) and save a buck or two when bought in the 3,6, and 8 pack flats. Allow retail to mix and match. Keep enticing all accounts to buy more, by offering price breaks. Wholesale should be sold by the flat trays, which you need to know how much fit in for all sizes. Keep sizes separate when pricing. We can keep brainstorming these ideas, I probably need more info on your markets. When they come to you at your farm or market, keep the price lower. That feels right to me. Consumers have to pay for the convenience of the store.
-Wooden trays- we would love to learn more about your construction techniques. We are really hoping to have wooden trays this year.
As far as the cedar flats are concerned:
Wholesale will not need these "cedar flats" as long as they do their own point of sale....If you do the point of sale for them, DON'T use cedar, as they won't be returned, you'll lose too much investment in time and money. Find a local plastic pot garden flat salesman with the size you need for 2" and 3" inch blocks to be sold in 6 packs.
Retail Hopefully, these are you own customers. There will be 3 main sizes for RETAIL: 2" 3", 4" That is because they will last longer on the shelves without worry of root space. I made cedar flats only for the 2 and 3 inch size: 1 size will fit all: 6-8--2" and 3--3" But, your system can be tailor made to whatever you're doing, I was doing vegetable starts only.
Size (Interior) Approx. 8-1/2" L by 4-1/4" W by 2-1/2" H. Why? You can easily load them with the Mini 4, and seed directly for most crops, and the space allows for air gaps that keep roots pruned. Many crops will be started in the 3/4" Micro 20 and transplanted into the 2 or 3 inch soil blocker and then hand selected and loaded into the cedar flat for retail.
Get the sawyer to make you the 8-1/2" boards, and you'll cut them up into the 3 pieces using a table saw with pre-marked clamps for your three sizes.
Use an air tack gun preferably with staples or copper nails for looks.
Its is assembly line type of stuff, but worth it.
Now you'll make the carrier flats, use a comfortable weight of the amount of 6 packs one can handle. I am strong, so I loaded my carriers up with 64 2" soil blocks which was 8-8 packs. That was a 18 by 18 inch tray! Too much weight, but the tray is all about the system. The system of transport, unless you got customers coming to your farm, but you never mentioned that. Truck farming soil block starts STARTS WITH THE TRUCK, and designing it to haul heavy soil blocks, so decide what the carrier trays will look like, what they will be trucked in and develop rack and shelving for easy loading and unloading.
It is a farm overhaul, I know...But consider this: You'll be the ONLY one doing it this way, you can charge higher money and get more customer by becoming a solution orientated service business. I guarantee the demand will outstrip your supply, so here's what you DO NOW: Design and build the system that right for you and your staff. We can work on that later.
Always charge a dollar deposit on the flats. Do not lend out carrier trays, continue to use the beer flats for multiple pack sales.
-Species- are there any species you do not grow in potting blocks? Any odd ones you do? Andy thinks corn potting blocks would be an interesting novelty. Do you do any multi-plant blocks like Eliot Coleman recommends (e.g. beets)? What about tomatoes- How do you deep set them into a 4" block?
I've grown and sold all species and varieties. But, to be profitable, you might want to follow the trends and markets, and keep an eye on Johnny's Seeds for ideas. Just don't skimp on the seed cost. The seed is the cheapest part of the whole system, and yet it is the most important. Its ok to buy the good ones! Corn is very sale able! I think 5 gallon bucket corn would sell all day, every day. That is container sweet corn. I used Orchard Baby, but there are others. Include instructions and market it.
Again, skip the multiplants for nursery sales.
Yep, deep set, but lets get technical for a minute: You won't have time "deep setting" a 2 inch block into a 4" block. Why? It requires smashing down the square hole another inch with your fingers, no, that won't do. All you have to do is this: Rotate the 2" block one turn and bury the stem on its side. DONE! NEXT! DONE!
We can talk further on the wood packs and trays, that is fun stuff. I will recall a few things here.
First this was an experience that moved from trial to serious demand, but was quickly replaced by the soil blocker tool business, so I did not "tool up" properly for a wood shop. I found that single brad nails are more attractive than staples. Use a small brad nailer air gun and pancake compressor. Size up the brads according to the thickness of your cedar. Mine were probably thinner than what your sawyer has, so go with what is recommended for that thickness, as I went with the smallest possible.
I used a table saw for everything, but perhaps a band saw would be better: saves material, cleaner cuts, quieter, etc..
I would tool up first, maybe investing in good tools, a dedicated wood shop and trained labor. If demand hits, you've got the supplies. Get your cedar sourced and make sure your sawyer does it just the way you like every time. Work with him to keep the cedar and sizes available. Soil blocks and seeds are the easy part, marketing and transporting with the wood tray system should be created properly from the start, as this will differentiate your farm and sales will boom.
I would have a custom made wood burning farm brand logo iron made for you now. Search the internet and invest in this. It is waaay too time consuming to do burn wood logos and letters on trays with a wood burning tool; take my advice!!!
-What sizes of seed trays did you use? We thought we would have a larger one that holds quite a few soil blocks on carts for our wholesale accounts. But of course also wanted to have smaller sizes for customers to buy smaller quantities of soil blocks directly at farmers markets, etc. and to have on a shelf below on our wholesale carts with the deposit system for the trays. Did you have standard tray sizes? What were your favorites?
I had two tray (pack) standard sizes: 6 pack of 2" blocks Or 8 1.5" blocks, and 8 pack of 2" blocks or 10 1.5" blocks, or 3 3" blocks. They are roughly 6.5" x 4.25" x 2.5", and 8.5" x 4.25" x 2.5" BOTH worked well, and sold well, although the 6 packs sold faster.
-How high were your soil block trays? This is what caused us to pause ordering the branding iron. I suppose we can experiment endlessly with the horizontal sizes of trays really, but the height will probably be fairly uniform. We thought the higher the side, the larger the brand could be so we wanted to see if you had a suggestions about a good height. Is slightly more than 2 inches good? Does a 1/4 inch extra help with anything such as transportation/stacking before they sprout, protecting the blocks, etc.?
2.25"-2.5" Yes, Yes. Remember, for seeding, the choice is yours if you want to start in wood, or start in plastic, hand pick the best and place in wood packs for sale. Then, wood packs go to transport via wood flats which go into the transport shelves in vans and/or shelves with casters.
-We are hoping to get 1/2" or less thick boards. Our sawyer said if we get 1/4" thick the only risk is that knots might slip out. I am tempted to try this option and consider knots when cutting down to size if necessary. My question is if I use 1/4" thick boards for the bottoms and sides, do you use a thicker board for the ends for nailing into for a more secure hold?
Yes, thinner boards go to the long sides, thicker short sides. Knots are fine if they aren't on the edges.
-I have been looking at brad nailers and pancake compressors. I also agree that brad nails look better than staples. Did you find they held as strongly as staples? When was talking to the people at the hardware store they were thinking maybe a brad nail in an 18ga nail gun would shoot right through a 1/4" cedar board. Did you use 1/2" brad nails? You did not use glue did you?
No, they do not hold as strong as staples. It was all about touch, and I used a brad nail gun using 20 gauge nails at 1/2". You’ve got to go easy on them, two or three to a side, 4-5 per side on bottom. I used to use glue. Again, way too much time, as customer weren't returning the trays, so yes, you are right in charging more and they can keep the tray!
-Did you heavily favor one block size over the other for retail? For example the 3" block? Just thinking for production terms of what to focus on.
MOST crops will sell in 2", greens in 1.5", and tomatoes, peppers, eggplant, celery, squash, melons, cukes are sold in 3" blocks. But, then again, have smaller tomato plant in 2" blocks in 6 packs and cheaper, giving people options and tracking sales to find out what the market is bearing. Focus on variety and price-points and let the customer sales speak, and adjust accordingly. If one can not afford the trial and error method, STAY WITH 2" SOIL BLOCKS, and offer high priced 4" soil block transplants of tomatoes and peppers only.
-You talk about 'European-style' seedling sales, but when I Google for images I'm coming up short. Could you offer some more direction/ do you have any images of your own that you think might be useful.
That was my slogan, and I don't have pictures of my artisan hand painted signs found at farmer's markets, grocery stores, and my own greenhouse locations. They sold with the farms I have owned. Sorry. However, after years of this, I am not convinced this is the slogan or name or title to give these soil blocks, it worked for me, but hasn't stuck around. But again, soil blocks themselves get way too lost in the American mind as being a construction technique. Why don't we both brainstorm this? By the way, what do think they could be called?
-What quantities of blocks per tray did you find worked best for each block size? We are going back and forth about how many blocks in each tray with relation to price point, etc. For example a 3 ct tray of 3" blocks might be $9. But that tray would be about 3/5"x9.5" or so. Quite small, but great if it sells!
3 and 6-8. Both fit in same size tray, as the 3" is only 3" on one side, 2.5 on the narrow side. So ideally, one large tray fits 6-8 2" blocks, 8-10 1.5" blocks, and 3, 3" blocks. Price point is all about LOOKS, if it looks like more greenery, it sells for more money. Even if the 3" blocks are only three, their roots are huge and the tops are bursting forth with lush greens. 9 is fine. That would mean perhaps making a spacious 6 pack of 2" go for 6.00. That should be about right.
I would suggest trialing out some packs, sizes, counts and crops with customers when you, yourself can interact with the customer and take a survey, narrow it down, and focus on the size/pack price point. Nail it down, and then roll it out.
-Did you offer a discount on pricing when a customer bought a tray vs. individual blocks? Is there an "incentive" to buy a tray or are the aesthetics the incentive?
All the same price IN the wood packs WHETHER you MIX AND MATCH, or not. Knock off the price of the wood tray IF you have other forms of packaging, or they bring their own. What I have found is that people will not be bring their own, or return the tray very often, so that you might as well have the large wood FLATS filled with Mix and Match crops, that sell IN a wood tray, or you have some cheap trays ready to go, either recycled containers or whatever, beer flats, etc. There is going to be a difference in customers regionally and locally based upon your clientele and their disposable income. I cannot say for sure who your customer is going to be, but if the extra cost of a wood pack is going to move like molasses, cut back on that and go for "beer flat" method. If high end gardeners are abound, go with wood, bill for the box, and they can have it!
-What did you charge for a deposit? I feel like a deposit should be small, much less than the product. However I also feel like we could turn around and sell our hand made, branded, wooden soil block trays for much more than we will probably charge for a deposit.
See previous answer to this direction, but I would say that, at this point, I would need to know about your customers, and proposed markets to be sure where exactly to guide you. Perhaps, varnishing them or something like that, putting a price tag on the whole tray with plants would be the best way to go? We want to remain competitively priced, with added-value for higher costs. Perhaps do something like this: Mix and Match in beer flat, with set-prices on certain sized blocks, AND 3 and 6 packs in wood branded wood trays for higher prices, but give them the BEST plants in the most popular varieties.
-Regarding saws I am wondering if a miter saw might be best. If we order our boards from our sawyer in the width and thickness we want, we should just have to chop them down to the lengths we want and nail them together. Is that correct? We won't really have to cut for height though.
Yes, miter it up! That's right.
Can you recommend a good box for blocking in and board for twisting the blockers on before pressing out the blocks in their flats? There are so many different bins and totes we thought we should ask in case you have a solid recommendation for one that works better than others. Is plywood good for twisting the blocker on to compress the blocks? Or is there something with a little less friction and more durable?
I have found large black cement tubs in the large Big Box Hardware Stores for mixing cement that works perfect!
Also, you can mix wet mix in an electric cement mixer.
Plywood, as you know, is not really recommended, unless you cover a nice piece with linoleum tiles, the kind that just peel and stick. That works well.
Fasten a strip of wood around the edge of a 2' x 2' plywood and it is good.
Another option is cutting the bottoms off large rubbermaid tubs, glue or screw to an overall larger piece of plywood for an anchor base that is wide.
Large Fiberglass trays are really nice, sold at hydroponic stores, but pricey.