Roll out 5 yards of upholstery fabric on a flat works surface, such as a table. Use a measuring tape to measure 16 inches of the fabric.
Measure the circumference of the chair and add an additional 8 inches for the four box pleats. Each box pleat, which is located at the corners, should be 2 inches long.
Cut the upholstery fabric with scissors using the measurements from the chair.
Position the short ends of the skirt so the wrong sides face each other to form a tube. Use needle and thread to stitch the two sides together. Fold the tube in half lengthwise, so the outside ends face each other. Use T-pins to hold the skirt in place.
Use a marker to denote the center line at one end of the skirt. Make the mark on the wrong side of the 2-inch designated pleat area. Make additional lines where each of the pleat edges meet. Fold the fabric so the two edge lines meet to form a box pleat. The end of the skirt should be located where the tube was sewn together.
Pin the pleats so the skirt edges meet with the edges of the slipcover. Use the needle and thread to stitch the edges of the skirt to the slipcover. Make sure the seams are even and trim excess fabric.