hiya. do you mean the woodworking plan? if so, you can just make a box by 45deg beveling the corners of four pieces 1/4" thick wood that's about 2" wide and whatever lengths and you can cut 1/4" rabbets along one edge of each to make room for a back board. A little wood glue and you're good to go. I'd get fancy and put in contrasting wood keys into the corners, too, but i'm guessing there's more to one of them than that.