Round picnic table, which can be a nice alternative to the standard quad, presents unique challenges in construction. But you can use an X-leg construction, as in other picnic tables to provide a solid foundation and a lasting framework. Arrange the five 2 x 12s coming together to form a square 60 by 60 inches, and glue in place. To secure them, lay the 2 x 4 inches 54 through the center of the tables, and securely fasten with screws. You must come to within three inches on each edge.
To build a round picnic tables are Find the center of the square corner to corner drawing lines and marking the intersection. Cut the line around the circumference of the puzzle to form the top of the table. Measure 20 inches outwards along the center boards 54 2 x 4 inches and use screws to attach two of the 2 x 4 inches 40 through the boards, in parallel with the center 2 x 4. These hold the board and provide a basis for the legs.
Measure the center of four of the five remaining 2 x 4 inches from each end 20, and drill a hole through the center of each 2 x 4. Then cut the ends of each of these four at an angle of 45 degrees so that the ends remain parallel, and can thus rest flush on the surface of the table and floor. Alignment 2 x 4 in two forms X, with aligned holes, support the remaining end 2 x 4 between them and use 6-inch screws to secure the leg-Xs to the 2 x 4, which will be a center brace. Place the legs on the table, one leg-X in each of the 40 inch 2 x 4 attached to the surface of the round picnic tables.