Don goggles and gloves.Temporarily place the insulation and plywood board onto the uncut muslin fabric. Make sure the fabric can wrap around to the back of the board by at least half an inch on the lengthwise sides (there should be plenty of wrap on the sides if you obtained 36+ inch fabric) by folding the unrolled side of the fabric over the board and measuring how much it extends from under the board. Roll out the fabric a little more and cut a portion equal to what you just measured on the opposite side of the board. Remove the plywood board and insulation. Iron the fabric to prepare it for stapling and lay it flat.
Put on goggles and gloves. Place the fiberglass insulation in the center of the fabric. Lay the plywood board on top of it and carefully square them together.
Pull the edges of the cloth over the plywood board one side at a time. Staple the fabric to the board at the center first and work back and forth to the outer sides of the flap, tightening as you go.
Hammer two short nails into the back of each acoustic panel a few inches below the top side, leaving some of the nail exposed. Wrap picture hanger wire around each nail head with a single taut wire running between the two nails. Knock on the wall of the recording studio room to search for studs (studs will have a non-echoing dull thud) and hammer the longer nails into them. Hang the acoustic panels onto the nails.