Place the two 2-inch by 12-inch by 16-inch boards parallel to each other and approximately 33 inches apart from the inside edges, with the 2-inch by 12-inch ends flat on the work surface. These are the bench seat legs.
Position the 2-inch by 12-inch by 36-inch board across the top 2-inch by 12-inch ends of the legs. This is the seat board. The outside of the legs should be flush with the ends of the seat board.
Drive four evenly spaced flush-trim wood screws through the top of the seat board into the ends of the legs at each joint, using a screw gun.
Center the 2-inch by 6-inch by 33-inch board between the legs so that the 2-inch by 33-inch edge is flush with the bottom of the seat board and the 2-inch by 6-inch ends are located against the inside of the legs. This is the cross support board.
Drive two evenly spaced flush-trim wood screws through the outside of the leg boards into the ends of the cross support board.
Apply a matching wood finish to the bench seat assembly with a poly brush. Allow the finish to dry at least four hours before handling and 72 hours before heavy use.