Maybe a simple support structure like this...I have (2) 4x4 growing trays that were used at pot growing facilities that DH will figure out a way to raise them up to hip height for me.
You could slap something like that together in no time. If your growing trays are 4X4 feet, you could probably build a support structure out of pallet wood. Just build it to your required height and size. Nice thing about that 2-part design is that you can easily relocate it if needed. Well, the growing trays might be too heavy to move unless you emptied them.
I'm not a fan of using wood around here, it rots too quickly, but maybe PT would be good for this project.

I like working with wood. The last year and a half I have made lots of rough, but useful, projects out of free pallet wood and salvaged lumber. If/when the wood rots, I'll just build a version 2.0 of the unit and probably make it even better.
