Position two 3/4-by-8-by-36-inch plywood boards with their long, thin sides on the ground, parallel to each other. Set a 3/4-by-8-by-48-inch plywood board against the end of the parallel boards. Arrange two metal L-brackets between each pair of boards. Drill out the bracket holes and attach the metal L-brackets with 3/4-inch wood screws. Repeat to add an additional board to the other side of the frame with 1-inch metal brackets.
Set two 3/4-by-24-by-37 1/2-inch plywood door boards on top of the frame. Set two side-mount cabinet hinges in between each door and a side board. Mark the bracket holes of each of the hinges on the door and the side board. Attach the hinges to the door and the side board with 3/4-inch wood screws.
Position a 3-part magnetic center latch in between the boards at the top of the cabinet. Mark the latch holes on the top board and each of the doors. Drill out each hole and attach the latch with 3/4-inch wood screws.
Set doorknobs against each of the doors and mark the location. Drill through the door at each marking. Slide the doorknob bolt through the door and attach it on the other side with nuts.
Use a stud finder to locate and mark each of the studs in the wall. Position the frame over the wall in the desired spot and set 1-inch metal L-brackets between the wall and the frame, with the brackets over marked wall studs. Have an assistant hold the frame against the wall. Mark each bracket hole and drill them out. Attach the brackets to the frame with 3/4-inch wood screws and to the wall with 3-inch wood screws.