Lay each assembly deck-side down. At the beanbag end of the board, drill a ⅜-inch hole through the center of each side piece 3½ inches down from the outside corner. Push a bolt through each hole and fit a leg onto the bolt inside the frame. Secure the bolt with a washer and nut. Tighten the nut until it's snug but not so snug that you can't fold it flat for storage.