Cut four 4-by-4-inch posts 28 inches long for the legs of the table. This is a standard height for a normal kitchen table. Adjust the length according to your height preference if necessary.
Measure two 6-feet sections from two 2-by-4-inch boards and cut to create four 29-inch supports. These will frame the table and add strength to the legs.
Find the center point in a 4-feet square piece of 1-inch plywood. Using a 3-feet long piece of string attached to a pencil, attach the end without the pencil to the center point of the plywood with a pin. Take the pencil and stretch it out as far as it will go and draw a circle around the center point of the plywood. The result should be a perfect 2-feet radius circle.
Use a circular or hand saw to remove the square edges of the plywood along the pencil marks. Smooth any rough spots and edges with a sander and sandpaper.
Place the table top on the floor and arrange the supports on it forming a square. Nail the support to the plywood with 2-inch nails spaced at least 4 inches apart. Place the table legs in the corners of the supports and screw them into the sides of the supports using an electric drill.
Paint or stain the finished table as desired. If you choose to stain it, seal it with a wood varnish.