Rest the 30 inch by 60 inch section of plywood horizontally, standing on the 60-inch edge. Align one 4-by-4 to each corner of the plywood along the edge that is resting on the ground.
Drive four nails through the plywood, two at each corner to join the 4-by-4 legs to the plywood table top.
Flip the plywood over so the opposite two corners are on the ground and repeat steps one and two to attach all four legs. Place table in standing position.
Attach the 2-by-4s to the inner edges of the four 4-by-4 legs.Align the base of each 2-by-4 to the base of the 4-by-4s and drive four nails into each section of 2-by-4 directly into the 4-by-4. The 2-by-4 will run vertically up the length of the 4-by-4 to create a strong base for the table shelf.
Lay one section of plywood on a flat surface in front of you. Measure out 4 inches from each corner along both joining edges. Mark each location using a pencil.
Line the inner corner of the t-square to the first corner's 4 inch marks. Draw a 4-by-4 square at the corner by tracing the inner corner of the t-square onto the plywood. Repeat this until you have a 4-by-4 square at each corner.
Cut away the 4-by-4 sections from each corner using the hand saw. This will create a passage for the 4-by-4 legs.
Attach this plywood shelf to the table by resting it on top of all eight 2-by-4 sections. Drive two nails into each 2-by-4 section through the top of the plywood.