Mary Dobson offers these simple instructions on how to make your own pleated cushions.

Pleated Cushions

Materials:

Fabric
Cushion form
Thread
Scissors
Grid
ruler
Measuring tape
Disappearing marker pen
Pins
Iron

Instructions:

Measure the cushion form and add 1 inch all
around for seam allowance and cut one layer for the cushion back to this size.

Determine the number and size of pleats required. In this
example, the cushion is being made with four pleats, each 1 inch deep. For each
pleat in this size, add 2 extra inches to the length of the cushion front
fabric in addition to the 2 inches for the seam allowance. The width of the
front fabric layer will be the same as the already cut back layer. Tip – Cut
this section several inches larger to begin and trim down to exactly match the
back layer once all of the pleating has been finished.

Working on the front side of the fabric, determine the
placement of the top pleat and move forward 1 inch. At this placement point,
mark a straight line across the width of the fabric with the fabric marker.
Repeat every three inches. Be sure to keep the line perfectly parallel with the
top cut edge.

Move an ironing surface and fold the fabric wrong sides
together along each marked line and press. Pin the secure and move to sewing
machine.

Pin to secure and machine stitch 1 inch in from the pressed
edge. Tip – the fabric may want to creep along as you sew so pinning is
important but you also can alternate the direction you begin sewing from.

Move back to the ironing surface and hand press the pleats
in the direction you would like them to sit and then turn pleats down on the
board and steam press for the back.

Place the cushion back layer right sides together with the
pleated front and trim as needed to make both layers the same size.

Machine stitch the two layers together and apply zipper to
bottom edge if desired.

Finish and trim seams and flip right side out. Press and
insert cushion form.

Alternatives:

For intersecting pleats add calculated width
and length to front section. Press and stitch all of the pleats in either the
length or the width and then work in the alternate direction.

For butterfly pleat,
press and stitch the pleats in place and then pull back the center of the
pleats and hand or machine stitch to secure.