Measure and cut three pieces of plywood, each 24-by-24 inches; these will be three sides of the cube desk. Sand each piece smooth, taking special care on all the cut edges to remove any small splinters or rough surfaces.
Cut four 24-inch lengths of aluminum brackets and drill 1/4 inch holes in both sides, spacing them 3 inches apart.
Select one piece of plywood to be the bottom of the cube. Lay one of the aluminium brackets along one side and screw in place, using 1/4 inch screws that are 1/2 inch long; this prevents the top of the screw protruding beyond the wood. Repeat on the opposite side of the base.
Stand a sheet of the cut plywood next to the base, aligned against it. Screw in place using screws through the holes in the upright in the aluminum bracket to make an "L" shape. Repeat on the other side to give a squared-off "U" shape.
Screw an aluminium bracket in place along the inside top of one arm of the "U," then repeat on the other arm.
Cut a piece of 3/4-inch plywood sheet so it’s 24-by-25 ½ inches. Line up with the three sides of the cube so it fits on top. Screw in place with screws through the holes in the aluminum brackets.
Measure the outer dimensions of one of the open ends of the cube and cut a piece of 3/4-inch plywood to size. Screw in place using 1 1/4 inch screws going through into the plywood sides of the cube.
Paint with a thin coat of wood primer and leave to dry.
Paint with acrylic gloss paint and a paintbrush. Leave to dry, then apply a second coat. Add a third coat to give extra protection and seal the wood fully. Leave to dry.