Rather than spend hundreds on plastic trays, I typically build my "tables" into the floor, and plug a drain at the low point.
Like I did in my veg room? It cost me about $30 in wood, and I can walk all over it.
I build my tables waist high, because human ancestors have only been walking upright for maybe a million years and our spines have not yet evolved to handle the load. Back pain is real. You will get older. Plan accordingly.
bend at the knees? I agree if I was gardening into my golden years this might be a concern... but I'm not even 30 yet and I've had the arthritis cut out of my body. I'm good to go! Gonna have a real career soon.
edit: 5' x 35' of 45 mil EPDM pond liner inbound... $150 shipped.
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