The solid wall is a bummer, but you just need to raise the plants to the height where they get the most sun. It looks like you've got it set up pretty well for one row.
If you want to go 2 deep, maybe use milk crates, cinder blocks, old wooden boxes, etc. Get anything sturdy like that with a uniform height, then stack them as high as you need, put the plywood on top. You can put an old sheet or tablecloth either over or under the plywood if you are worried about guests, roommates, or your significant other thinking the base is ugly.