That looks great. I was going to rebuild my composite raised beds with something more sturdy. I was going to go with concrete boards like they use for tile (3’ x 5’) and reinforce them but this looks cheaper and just as durable. Have you thought about going 2 or 3 panels high? That’s probably what i would be looking at.
Initially I thought the one foot height was too short but after filling them, I realized higher sides would need more bags of soil/humus/manure so the higher sides would cost more and cost more to fill.
I did get humus/manure 2 cu ft bags at Walmart for $1.88 earlier this year and was able to fill this bed, but that price no longer available...
I have been composting a huge hill of fallen leaves and grass clippings from last year. I’ll try to fill the two new beds with that. I’ll put tomatoes, cukes and sweet potatoes in them this week.
Bob; You could look at some 24” Wide galvanized roofing panels from Home Depot, buy 3, use 2 for the sides and cut the remaining to 36” or 40” inches. Good luck!
https://www.homedepot.com/b/Building-Materials-Roofing-Roof-Panels-Metal-Roofing/N-5yc1vZapwh