Form four planks of 24-inch 1-by-6 lumber into a rectangle-shaped frame. The ends of two opposite planks should rest on the inside edge of the other two planks to form the corners of the frame and make the outside dimensions 24-by-26 inches.
Glue the frame together and set it into corner clamps while the glue dries, so the frame keeps its shape.
Drill three pilot holes, sized for the shanks of 2-inch wood screws, through each corner joint of the frame and fasten the frame together with 2-inch wood screws through all the pilot holes.
Apply wood glue to the top edge of the frame. Sit a piece of 24-by-26-inch, ½-inch plywood on top of the frame and press down to glue it in place. This is actually the base of the desk compartment, but it is easier to attach it from the top.
Drill pilot holes for 2-inch wood screws every five inches around the edge of the plywood and secure the plywood to the frame with the wood screws through the pre-drilled holes. Turn the frame over, so the base is on the bottom. It will look like a drawer or a box without a lid.
Paint the desk compartment, as well as four planks of 28-inch 2-by-4, which are the desk legs, and a sheet of 26-by-30-inch 1/2-inch plywood for the desktop. Painting the desk before assembly is much easier than when it is all screwed together.
Turn the desk compartment back over, so that it is plywood-side up again. On each of the 24-inch sides of the compartment, position a leg flush with each of the compartment corners. The legs should be sitting upright. Use G-clamps to hold the legs in position.
Pre-drill four pilot holes through the legs into the sides of the compartment, positioned like the number four on the sides of dice and sized for 2-3/4-inch lag bolts. Attach the legs to the compartment with the bolts through the pre-drilled pilot holes. Turn the desk back upright so it is standing on the legs and the open side of the compartment is facing up.
Center one half of a 24-inch piano hinge along the back edge of one of the desktop’s 30-inch sides. Secure the hinge to the desktop using 1/4-inch screws through each of the pre-drilled screw holes in the piano hinge.
Center the desktop over the top of the desk compartment, with the 30-inch side of the desktop parallel with the 26-inch side of the compartment. Adjust the position so that the back of the desktop with the hinge attached is flush with the back of the desk compartment. There will be two inches over at the front of the desk.
Secure the second half of the piano hinge to the back of the desk compartment using 1/2-inch screws through all the screw holes in the piano hinge. You will now be able to lift up the desktop and access the storage space in the desk compartment underneath.