Cut four 2-by-4-inch boards 29 inches high. Cut two 2-by-4-inch boards 24 inches long. Cut two 2-by-4-inch boards 36 inches long.
Place the 36-inch boards on a level surface with the 2-inch edge turned up about 20 inches apart. Position the 24-inch boards perpendicular to the ends of the first two boards, creating a rectangle with the dimensions 24 by 40 inches. (This may not be perfectly exact because 2-inch milled lumber is usually about 1 3/4 inches wide rather than a full two inches.)
Nail the corners together with 8 penny finishing nails. Use a countersink to drive them slightly below the surface.
Stand the 29-inch boards on the inside of the rectangle, one at each corner. Position them so the 4-inch side is flat against the 36-inch side of the rectangle and the 2-inch side is against the 24-inch side. Attach them temporarily by driving one nail into the short side through the outside of the rectangle into the 29-inch board.
Drill two holes through the long side of the rectangle through the flat side of the upright board, being careful to avoid the nail you just drove in to hold the board in place. Recess the outside hole slightly with a paddle bit. Use two bolts to secure the upright to the long side. Repeat at each corner.
Cut another 2-by-4-inch board 36 inches long. Cut two 2-by-4-inch boards 24 inches long. Position the 36-inch board on the long side of the structure, about half way down the uprights. Use C-clamps to hold it in place. Make sure it is level. Drill two holes in each end through the 36-inch board and through the uprights. Sink the holes slightly with a paddle bit. Secure with bolts. Nail the 24-inch pieces on the ends (be sure they are level). Countersink the nails.
Turn the structure over so the ends of the uprights are on the ground and the rectangle is on top, where it will act as the base of the table top.
Cut 12 1-by-3-inch pieces of wood 26 inches long. Mark the center on each one and then mark the center on each narrow end of the frame. Position these pieces on the top frame, using the marks to help center the boards. Use a nail or other item to measure the spaces between the boards so they are consistent. Allow the end boards to extend slightly beyond the edge of the frame on each end.
Nail the 1-by-3-by-26-inch boards to the top of the frame when you are satisfied with the spacing. Countersink the nails.
Mix sawdust with white or carpenter's glue. Fill the nail holes and the countersunk bolt holes with the mixture. Allow it to dry.
Sand or rasp rough edges. Sand down the sawdust filling. Paint with a clear finish or a color as desired.