Stacked concrete blocks work pretty well for gardens. You can line them with plastic on the insides and weed mat across the bottom to save water and keep the weeds out. I like to fill the holes in the concrete blocks with soil and rebar. The walls are vertical so folks can garden from a wheelchair if they want. With a short hose at the end of the garden, watering can also be done from a wheelchair, too.
If you're building one for a wheeled gardener, have them out where you're building the garden so it can be made to fit their reach. Bring it up to a comfortable level for them and make it as deep as they can reach in from either side. A garden like this can be amazingly productive and even help lower food bills so it can be a comfort to more than the gardener.
We're using the same sort of garden construction, but for us it's sort of being used to terrace a hillside so only one side can be accessed via wheelchair. Built on a flat spot, it would be accessible from both sides.
It's stacked blocks, screened top soil from the yard for most of it, soil and rebar in the holes of the blocks. There's weed mat across the bottom, and the top foot of soil is amended with your choice of fertilizer and amendments. We use bunny manure and crushed oyster shell.
There it's finished and seeded and fenced on three sides to keep out chickens, you may not have a chicken problem in your location, though.
Three and a half weeks later, it has been weeded for the first time. Had the soil been sterile soil bought from a store, it probably wouldn't have had any grasses and weeds in it. Or, if I would have let the weeds and grasses grow and then either tilled them under or pulled them out, then I'd not have to pick them out from among the lettuces. But, it's easy enough to pick out tiny weeds when they are this easy to reach.