Lay the 6-foot-long 2 x 4s flat, measure them with measuring tape and draw a line with a pencil at 36 inches. Cut the board at the mark with a saw, then sand the edges.
Draw a line down the center of the 36-inch boards. Mark eight Xs on the line on each board, spacing the marks every 4 inches. Leave a 2-inch border on each end to leave room for screws to fasten the boards in place.
Drill a half-inch hole on every X from step 2 using a half-inch drill bit and a hand drill. Use a drill press for a more accurate and straight hole.
Cut two pieces of 1 x 1 lumber to 22 inches, as the 2 x 4s were cut in step 1, then sand the edges. Cut the PVC pipes or plastic dowels to 12 inches using a PVC pipe cutter or a hacksaw.
Make a square with two 2 x 4s (4-inch side up) and two 1 x 1s. Put the 2 x 4s on top of the 1 x 1s so the 2 x 4s are elevated off the ground tol allow the boots on the rack to dry quickly.
Apply wood glue to any place that the wood touches, turn the wood square upside down, then drill two 2¼-inch wood screws into each corner through the 1 x 1 and into the 2 x 4. This hides the screws from sight.
Apply PVC cement to the ends of the PVC pipes and insert them into the holes. Once the boot rack is dry, hang the boots upside down from the top of the rod.