Steps: 1. Using a table saw, rip some 2x4s lengthwise to make 2x3s (actual measurement will be 1-1/2 by 2-1/2). Cut two 16-1/4 inch side pieces and two 57-inch pieces from the 2x3s. Use a dado blade on the table saw to make rabbit or lap cuts on each end of the 57-inch boards (figure B). Always be sure to wear safety goggles and a dust mask when working with power tools.
2. The seat of the swing will have a slight angle toward the back. Taper the side pieces from 2-1/2 inches to 2 inches in the back. Mark one end of the side pieces at two inches and use a straightedge to draw a line to cut for the taper (figure C). Cut the tapers with a circular saw.
3. Rip one of the 57-inch boards down to two inches wide to match the side pieces (figure D).
4. Counterbore and pre-drill two holes in the front ends of each side pieces and one hole at the back end of each piece (figure E). Attach all four pieces with glue and lag bolts to make the seat frame (figure F).
5. Cut two 14-inch lengths of 2x4 to serve as the seat supports. Rip the supports after cutting to match the taper of the side pieces (2-1/2 inches in the front, 2-inches in the back).
6. Position the supports at 19 inches on-center from the ends and attach with glue and wood screws (figure G). Use two screws at each end of both supports.
7. Make the seat slats by cutting 1x4s to length (57 inches) using a miter saw . Take those pieces to the table saw and rip them down to 2-1/2 inches wide. Use a router with 1/2-inch round-over bit to take the edge off and create a nice radius edge. Finally, smooth out slats with a random orbit sander.
8. Attach the slats starting in the back, making sure the edges are flush (figure H). Attach by spreading a layer of wood glue on the bench, then secure with finishing nails. Use two nails at each juncture between the frame and slats and be sure to sink the nail heads with the nail set.
9. Cut 1/2-inch spacers out of scrap wood and use to ensure a nice, even spacing of slats. Overlap the front slat by about 1/2-inch (figure I).
10. Now start making the back. Begin by cutting frame members. Cut two 57-inch lengths of 2x4s and two 18-inch lengths for the sides. Use the dado blade to make lap cuts to join the frame pieces, and check to make sure everything is square (figure J).