Building a picnic table consists of three steps: cutting the parts of the frame, assembling the frame, and installing the seat and table tops. You need three 2x8s, nine 2x6s, three 2x4s, eight 3/8 x 3 1/2-inch carriage bolts, eight 3/8-inch washers and nuts, and 2 1/2-inch deck screws.
Use the 2x8s to cut four legs while mitering the ends of each leg at 22 degrees. Cut two 2x4 crosspieces for the top and two 2x8 crosspieces for the benches, two 2x4 braces with the ends mitered to 45 degrees and 2x4 braces for the middle of each bench and the tabletop. Attach a crosspiece to each set of legs using the 2 1/2-inch deck screws and each bench's crosspiece to the legs using the 3 1/2-inch carriage bolts.
For the length of the benches and the tabletop, cut two pieces of 2x6 for each bench and five pieces of 2x6 for the tabletop. Attach the bench tops to the bench cross-frames using the 2 1/2-inch deck screws while standing the a-frame sides up, then repeat the procedure for the tabletop planks with the same screws. Leave approximately 1/4 inch between each plank. Use screws to attach the 2x4 braces to the bench crosspiece and the underside of the tabletop. Finish with deck stain if desired.