Cut four pieces of plywood, one four each wall. Plywood is the main material for your recording booth walls. The thicker the wood, the more insulation it provides. Aim for at least 1-inch thickness. If necessary, nail two pieces together. Each piece should be the same height. The size of your room dictates the maximum height, but make the walls so that the tallest member of your band can comfortably stand in the booth without stooping.
Make each wall a different width. The smallest must be no smaller than 24 inches wide and the largest no greater than 56 inches. Equally sized walls create a perfectly square recording booth. This shape is not desirable because irregular-size walls reduce sound reflection more effectively.
Cut eight pieces of narrow wood, each no longer than 5 feet. These will form the support legs that hold the boards up.
Staple an old bed sheet to one side of the plywood. The sheet adds an extra layer of insulation to the booth and makes it easier to attach the dampening material. Place the sheet on your workbench. Lay the board on top, and smooth out any creases. Fold the edges of the sheet over the edges of the board and use a staple gun to fasten them down.
Cut egg cartons in half. Egg cartons make excellent dampening material. The peaks and dips create a very uneven surface which absorbs sound and limits reflection. Use a pair of scissors to cut the cartons in half along the hinge between the lid and the base.
Cut foam squares to irregular sizes. If you can't get enough egg cartons to cover the inside of your booth walls, foam squares are also suitable. Use a serrated knife to cut the foam pieces so that they are irregular lengths, between 4 and 7 inches.
Coat your dampening material in flame retardant using a paint brush. While it adds nothing to the acoustic properties of the dampening material, both egg cartons and foam squares are highly flammable.
Fit a rubber foot to one end of each support leg, these feet are available from most hardware chains. These stop the legs from slipping on the floor. If necessary, use a piece of 80-grit sandpaper to shape the base of the legs to fit the feet. Screw a hinge onto the other end of each support leg, and then screw the hinges to the back of the wall, no higher than 5 feet from the top. This props the wall up from the rear. To give yourself positioning options, it's smart to make the booth walls free-standing.
Bend a wire coat hanger into a horseshoe shape. Wrap two pairs of thick pantyhose around the loop and fasten them on with clothes pegs. Coil the nonlooped portion of the coat hanger around the stem of the microphone stand and position the loop in front of the microphone. This improvised "pop-shield" reduces sibilance, the unwelcome hiss created when you make an "s" sound too closely to a microphone.