If you’re going to make a raised bed, make a raised bed! This took 9 landscape timbers each measuring 6″x6″x8′; 3 per side were used to make the 8′ length, the remaining 3 were cut in half to make the 4′ width.* The brackets were made for me by the local tech high school; each measures 12″x14.5″x3/16″, the bend occurs at the 3″ mark of the long side. Holes were drilled 1″ either way from the top, bottom and side edges with the third hole evenly spaced between; each hole accommodates a 3″ wood screw.
If you’re building these yourself, they’ll run about $200 for materials, including the compost to fill them ~ worth every dime, as they require no bending for installation or maintenance. The edges are fat enough to afford reasonably comfortable seating for planting or weeding and the width (2′ from either side) makes them usable, with proper surfacing of the surrounding ground, by wheelchair gardeners.
*You could get fancy and do a greek key pattern, but the brackets are so sturdy I didn’t bother.