Start with four (4) 1” x 6” x 8’ cedar decking planks. Use a miter saw to cut them into eight pieces 1” x 4” x 36”.
Use a table saw to rip 1/4″ off of both edges on those eight pieces. This removes the rounded edges, and leaves you with a nice square edge on each piece. They will also be 5″ wide.
Use a router and a 1/2” rabbeting router bit to remove half of the thickness on one long edge of each plank.
Use an exterior wood glue to glue two of the planks together – creating a rabbet joint. You’ll do this four times, gluing two boards each time. These will be your side planks.
After you glue each side, use the bar clamps to keep them together. Let them dry overnight.
You’ll now be working with the three 1” x 4” x 8’ cedar decking planks. Use a miter saw to cut six (6) 1” x 4” x 36” planks (you’ll have wood leftover).
Use a table saw to cut two of those six pieces in half lengthwise. Set those aside.
On the remaining four (4) 1” x 4” x 36” planks, use a table saw to take 1/2” off of one edge. At this point they will be around 1″ x 3″ x 36″, with the removal of 1/2″ of material as well as shrinkage.
Grab the four side planks from the first part of the project. Place one side plank face down. Next, place a bead of glue a 1/2” up from what will be the bottom edge of the side plank. Place one of the 1” x 3” x 36” planks onto the bead of glue squared edge down. Place it 1 1/2” lower than the bottom edge of the side plank and clamp.
Drill pilot holes. You’ll use a drill and a 7/64” drill bit along with a 3/8″ countersink drill bit to countersink each pilot hole. Place the pilot holes every 6”. Alternate the pilot holes 3/8” and 7/8” from the top edge of the foot plank. Using 1 1/2” long wood screws, screw down. Repeat steps 9 and 10 with the other three side pieces.
Grab your four 1″ x 2″ x 36″ planks for this step. Add a thin bead of wood glue 1 7/8” from the top edge of the side plank. Place one of your 1”x 2”x 36” planks on the bead of wood glue with the squared edge 7/8” from the upper edge of the side plank. Clamp into place.
Do as you did before and drill pilot holes every 6” down the center of the plank (countersink if you choose to). Use 1 ½” wood screws to attach the plank. This will be your upper support plank. Repeat with the other three side pieces.
Use a table saw or a miter saw with a pivoting head to cut 45 degree edges on both ends of each of the four side pieces.