Cut the pillow back 1" (2.5 cm) wider than the front to allow for 1/2" (1.3 cm) seam allowances at the closure. To center the closure in the pillow back, fold the pillow back panel in half, right sides together.
Center the zipper on the folded edge. Mark the fold at the location of the zipper stops. Stitching 1/2" (1.3 cm) from the fold, begin at one edge and stitch to the mark, then backstitch. Stitch to the opposite mark using a basting stitch. At the mark, shorten the stitch length and stitch to the edge, then backstitch.
Cut along the fold and press the seam allowances open.
Center the closed zipper facedown over the seam, with the stops at the marks. Pin the tapes to the seam allowances or secure them in place with double-sided basting tape. Finish the seam allowances with zigzag stitches, catching the zipper tapes in the stitching.
Spread the pillow panel flat with the right side up. Mark the top and bottom of the zipper teeth with pins. Center a strip of transparent tape, measuring 1/2" (1.3 cm) wide, over the seam from pin to pin. Use a zipper foot and topstitch along the edges of the tape to create a rectangle.
Finish the pillow, following the general instructions for the pillow style. Rather than leaving an opening for turning, open the zipper before stitching the final seam. Turn right side out through the zipper opening, insert the pillow form, and close the zipper.
This sewing tutorial is excerpted with permission from <a href="http://amzn.to/1hLUVHM">"The Complete Photo Guide to Slipcovers, Pillows, and Bedding"</a> by Karen Erickson and Carol Zentgraf and published by Creative Publishing international.