Lay the best sides of the five slats facedown on a flat work area, side by side.
Place 1/4-inch-thick pieces of scrap wood in between each slat as spacers. Line up the ends of all the slats evenly. Place a bar clamp across the center of the slats. Tighten it to secure all the pieces together.
Stand the 27-inch-long, 2-by-4-inch cleats upright on your work surface. Round off the top corners of each with a belt sander.
Measure in 12 inches on each side of the tabletop slats. Mark the spots with a pencil. Place the cleats on edge with the rounded-off edges facing upward. Place a cleat on each end of the slats, on the 12-inch marks.
Drill through the cleat and into the underside of each slat in the tabletop, using a countersink bit installed in a power drill. Drill two holes for each slat. Secure the cleats to the slats with 4-inch wood screws, driven in with a Phillips screwdriver.
Loosen and remove the bar clamp from the finished tabletop. Remove the 1/4-inch wood spacers from in between the slats.
Mark a 38-degree angle on the end of each 36-inch-long, 2-by-4-inch leg. Make the diagonal cuts with a circular saw.
Cross two of the legs to form an "X" at their center. Secure the legs with a C-clamp. Spread the legs so they are 28 1/2 inches apart at the ends. Make a pencil mark at the center of each leg where the other intersects it. Remove the C-clamp.
Cut laps in between the pencil marks at 3/4-inch deep with a circular saw. Put the legs back together and secure in the center of the "X" with a 3 1/2-inch carriage bolt, washer and nut. Repeat this procedure for the other two legs.
Secure the legs to the cleats on the underside of the completed tabletop with two 3 1/2-inch carriage bolts, washers and nuts each.
Cut two leg braces 16 inches long from 2-by-4 stock. Cut the end of each brace at a 45-degree angle with a circular saw. Attach a brace to the underside of the tabletop and to the center of one set of legs with two 4-inch wood screws on each end. Repeat this procedure for the other brace.