Begin by cutting off a 10-in. length of the board and setting it aside. Rip the remaining 38-in. board to 6 in. wide and cut five evenly spaced saw kerfs 5/8 in. deep along one face. Crosscut the slotted board into four 9-in. pieces and glue them into a block, being careful not to slop glue into the saw kerfs (you can clean them out with a knife before the glue dries). Saw a 15-degree angle on one end and screw the plywood piece under the angled end of the block.
Google is probably the first place where most people would start searching for woodworking plans, but often the top results can be a mix of articles and how-to pieces that just aren’t detailed enough. Sometimes they’ll link to the plans (like we try to here at Lifehacker), but other times, they’re just showing off a cool project. There are better, more precise ways of finding what you’re looking for.