Steps: 1. At home center or lumberyard, handpick eight perfectly straight kiln-dried 2x4s. Avoid any board with excessive knots or defects. 2. Select one 4x8-foot sheet of ¾-inch-thick B-C fir plywood. Check to be sure the plywood edges and corners aren’t damaged. 3. For convenience, have the plywood cut to size by a home center employee at the panel saw.