Sketch out a diagram of a trapezium and plot the lengths of each side according to the space available in your studio. Your vocal isolation box should have sides that are non-parallel and of irregular lengths. Parallel, equally sized sides reflect sound more readily than irregular sides.
Cut four pieces of plywood, equal in height but different widths. The walls are free-standing, so it’s fine to have overlapping sides.
Lay a bed sheet out flat on your work bench. Place the first board on top. Fold the corners of the sheet over the edge of the board and use a staple gun to fix it into the top-facing side of the board.
Drill a hole in one side, approximately 3 inches from the base, large enough to feed through the jack of an XLR cable.
Measure the length of the hinged support rail leg and plot a mounting hole for the bracket. It should be no more than an inch higher from the base than the length of the leg. Use a standard electric drill to screw the bracket onto the back of each wall panel. Determine the size of the drill bit according to the size of the screws. The leg support makes the walls free-standing. This renders the vocal booth easily transportable.
Glue egg trays onto the sheet on the inside of each wall. The peaks and dips in the surface of the egg tray absorbs sound and limit reflection. This dampens the inside of the vocal once constructed.
Stand up three of the four walls, so that their edges touch. Stand the fourth wall in place, but sufficiently ajar to permit access in and out. You’ll slide this wall flush against the others when the singer or other sound source is in the booth. Put the microphone stand in the narrowest corner. Slot the microphone into the microphone stand collar. Feed an XLR cable through the hole and connect it to the microphone.
Drape a sheet over the top of the booth and staple it to the back of each wall. Don’t pull it tight, allow it to hang loose over the top.