Position a pair of 3/4-by-24-by-36-inch melamine boards on their long, thin sides, parallel to each other, 22 inches apart. These are the side boards.
Place a 3/4-by-22-by-24-inch melamine board against either end of the side boards, to be the top and bottom boards.
Space 2-inch metal L-brackets between each board on the inside of the frame, 6 inches apart. Mark each of the bracket holes. Drill the holes. Attach the brackets to the boards with 3/4-inch wood screws.
Lay a 3/4-by-22-by-37 1/2-inch melamine board on the working surface to be the rear board.
Set the cabinet frame on the rear board. Space 2-inch metal L-brackets between the rear boards and the frame, every 6 inches. Mark the attachment holes. Drill out the holes. Attach the brackets with 3/4-inch wood screws.
Set a 3/4-by-22-by-37-inch melamine board on top of the frame to be the door.
Slide two evenly spaced side-mount metal cabinet hinges between the door and one side board. Mark the spots for the hinge screw holes on both the door and side board, removing the door if necessary. Drill out each hole. Attach the hinges in place with 3/4-inch wood screws.
Set a magnetic latch between the door and the opposite side board to the hinge side board. Mark the latch attachment holes. Drill out the marked holes. Attach the latch with 3/4-inch wood screws.
Set a 3/4-by-20 1/2-by-24-inch melamine shelf board inside the cabinet at a desired shelf height. Position 2-inch metal L-brackets underneath the shelf board against the shelf, rear and side boards. Mark the bracket holes. Drill out the holes. Attach the brackets with 3/4-inch wood screws. Repeat as needed for additional melamine shelves.