Secure Auralex, thick carpeting, or other sound absorbing material to each plywood piece.
Build Box A. Box A will use three 78-inch by 48-inch plywood boards for the walls of the box and a 48-inch by 48-inch board for the top of the box. Attach the 78-inch sides of two 78-inch by 48-inch plywood boards together using two metal hinges. These are the first two walls of Box A. Attach the 78-inch side of another 78-inch by 48-inch plywood board to one of the walls using two hinges. These three boards are the three walls of Box A. Attach the 48-inch by 48-inch board to the top of all three boards using two hinges per joint. Your box will have three walls and a ceiling.
Build Box B. Box B will use a 72-inch by 42-inch and two 72-inch by 48-inch plywood boards for the sides of the box and a 48-inch by 42-inch plywood board for the top of the box. Attach the 72-inch side of a 72-inch by 48-inch board to the 72-inch side of a 72-inch by 42-inch board using two hinges. These two boards are the first two walls of Box B. Add the third wall by attaching the 72-inch side of another 72-inch by 48-inch board to the 72-inch by 42-inch board using two hinges. These three boards are the three walls of Box B. Attach the 48-inch by 42-inch board to the top of the three walls using two hinges per joint.
Slide Box B halfway inside of Box A. There is enough room to fit a microphone cable and a power cord for a light or fan between the boxes. Make sure that the vocalist, microphone, and light are inside of the boxes when you slide them together. The hinges make the booth easy to tear down and move if necessary.
Find a closet that isn't in use.
Place Auralex, thick carpeting, or soundproofing material on all of the walls, the ceiling, and the door. Place a carpet on the floor if it isn't carpeted.
Run a microphone cable under the door.