Mark and cut the tops of the risers. Use your chalk box to snap a chalk line, lengthwise, down the middle of one of the sheets of plywood. Snap five parallel chalk lines that are each 16 inches apart along the long edges of the plywood. The chalk lines will have created 12 identical rectangles that are each 16 inches wide and 24 inches long.
Use a pencil to label these 12 pieces "A." These pieces are the tops of your 12 risers. Use a circular saw, or table saw, to cut the plywood using the chalk lines as a cutting guide.
Mark and cut the fronts and backs of the risers. Snap a chalk line, lengthwise, down the middle of the second piece of plywood. Snap 11 parallel chalk lines along the long edges of the plywood that are each 8 inches apart along the long edges of the plywood. The chalk lines will have created 24 identical rectangles that are each 8 inches wide and 24 inches long.
Use a pencil to label these 24 pieces "B." These pieces are the fronts and backs of the 12 risers. Use a circular saw, or table saw, to cut the plywood using the chalk lines as a cutting guide.
Mark and cut the sides of the risers. Snap three lengthwise chalk lines, each 14 1/2 inches apart; each section will measure 14 1/2 inches by 96 inches. Snap eight parallel chalk lines that are each 8 inches wide along the long edges of the plywood. The chalk lines will create 24 identical rectangles that are each 8 inches wide and 14 1/2 inches long, plus some scrap plywood.
Use a pencil to label these 24 pieces "C." These pieces are the sides of your 12 risers. Use a circular saw, or table saw, to cut the piece of plywood into 24 rectangular pieces using the chalk lines as cutting guides.
Purchase or rent a cordless 16-gauge finish nailer to assemble the risers using wood glue and 2 1/4-inch finishing nails for the power nailer. Ask a friend to help you by holding the wood while you assemble the risers using the power nailer.
Assemble the risers in a location so that the pieces of wood butt up against a wall or another immovable object. Power nailers need to nail into objects that will not move. Use sandpaper and a sanding block, or a power sander, to smooth the rough edges of the plywood pieces. Make sure to put the smooth side of the plywood on the outside when assembling the risers; plywood has a smooth and a rough side.
Create riser bases by building a frame that is 8 inches tall, 24 inches wide and 16 inches long -- the "B" and "C" pieces stand on edge, and the "C" pieces are inside of the "B" pieces. Run a thin bead of glue along one of the cut, short ends of a "C" piece. Place the glued end on the inside edge of a "B" piece so that it makes a 90-degree angle. Nail the "B" piece to the "C" piece using the brad nailer -- nail 3/8 inch from each end, and then approximately 4 inches apart.
Repeat Section 2, Step 3 on the remaining three corners of the riser base. Assemble all riser bases in this manner.
Run a bead of glue around the top of the riser base. Attach the top of the riser to the riser base by placing the rough side of an "A" piece on top of the glued edge of the riser base. Nail the riser top to the riser base using a brad nailer -- nail 3/8 inch from each end, and then approximately 4 inches apart. Repeat Section 2 to assemble each of the risers.
Spread the plastic drop cloth. Apply two coats of paint to each riser. After paint dries, apply L-shaped adhesive felt pads to the bottom corners of the risers.