Place the rough-sawed board flat on a work surface. Sand the board, using a sander that is equipped with a fine-grit sanding pad, in the same direction as the wood grain until the board is completely smooth.
Stand the four 2-by-2-by-18-inch hardwood boards upright so that one 2-by-2-inch end of each board is resting flat on the work surface. Position the boards so that one board rests in each of the four corners of the 2-by-18-by-32-inch board. These are the bench legs.
Lay the 2-by-18-by-32-inch board flat over the top 2-by-2-inch ends of the legs. This is the seat board for the bench. Drive decorative head screws through the seat board into the ends of the legs with a screw gun. Use two screws per leg joint.
Center one 2-by-2-by-14-inch board between the legs at each 18-inch end of the seat. Position the boards up 6 inches from the work surface at each end. These are the side support boards. Drive two decorative head screws through the legs into the ends of the side support boards.
Position the 2-by-2-by-28-inch boards between the legs on the front and back 32-inch sides of the seat. Position these boards up 6 inches from the work surface and fasten them in place the same way you did the side supports in Step 4. These are the front and back supports.
Wipe off the bench assembly with a tack cloth. Brush on an even coat of shellac using a natural bristle brush. Allow the shellac to dry for 24 hours and apply a second coat. Wait 48 hours after the final coat of shellac before you use the bench.