Cut three rectangular pieces of MDF for the walls. Each should be six feet long; cut the first piece one foot wide; the second, one foot, three-inches wide; the third, one foot, five inches wide. Smooth the edges with 80-grit sandpaper. Equally sized walls are bad for recording booths; they allow for more sound to bounce around the booth. The three walls will be free-standing, and the rear of the booth will be covered with a drape; the walls can be repositioned depending on the acoustic characteristics of the room.
Furnish the inside of the booth walls. Cut foam blocks of varying heights; the uneven surface on the inside of the booth will further reduce sound reflection. Cover the insides of the walls with glue and press the foam pieces into it to secure.
Lay each board on the floor, foam side down. Screw in the locking-hinge leg brackets to the outside. Fit the leg to the bracket and stand the wall up; the leg will swing back from the bracket and support the wall. Fit each subsequent bracket at a different height so that each wall has tilts at a slightly different angle to the other. Stand the walls up with the foam facing in. Ignore any small gaps between the edges of the walls. Position the booth walls so that they are close to and facing a wall in your room. Leave sufficient room between the booth edges and the wall for a person to get in and out.
Drape a large sheet over the top of the walls so that it hangs down and covers the empty side. Staple the sheet onto each wall to hold it in place. Cut a slit along the middle of the sheet so people can get in and out. Using a sheet instead of a fourth wall reduces the sound insulation, but it is considerably easier than building a hinged door.
Put a microphone stand in the center of the booth. Feed the microphone cable through the slit in the sheet and connect the mic.