I can’t remember where, exactly, I got these directions, but they have been well-used. I am sorry that I can’t refer you to the book, but this photocopy has been with me for 7 or 8 years. But, it is tried and true and easy to follow.
If making a rectangular cushion, exposed on all sides, cut a cushion top and a cushion bottom, with the length and width equal to the desired finished length and width plus 1”. If the cushion will be welted, cut fabric strips for the welting with the length equal to twice the circumference of the cushion plus additional length for seaming strips, joining ends, and inconspicuously positioning seams. Here is my old sofa cushion – the first I ever made.
Sometimes I find it helpful to make a pattern out of butcher paper, especially when you are dealing with a large print.
Next, cut the boxing strip. If the original cushion insert will be used, measure the width of the original boxing strip between the seams and add 1” for seam allowances. For a cushion with a zipper closure, cut the boxing strip with the length equal to the measurement of the front and sides of the cushion. Excess length will be cut off during construction. If seaming will be necessary, allow 1” for each seam, planning the placement of the seams out of view along the sides of the cushion. If continuous zipper tape is used, cut the zipper tape with the length equal to the back cushion measurement plus 8”, or purchase an upholstery zipper with this approximate length. Cut two fabric strips for the zipper closure, with the length of the strips equal to the length of the zipper tape and the width of the strips equal to half the cut width of the boxing strip plus 3/4”.
My fabric had a very large pattern, so I lined up my boxing strip to make sure that the pattern would “flow” well from the seat to the front of it.
Here is the cushion top, boxing strip and 2 strips for the zipper.
Next, sew welting around outer edges of cushion top and cushion bottom.
Press under 3/4” seam allowance on one long edge of zipper strip. Position folded edge of strip along center of zipper teeth, right sides up. Using zipper foot, topstitch 3/8” from fold. Repeat for opposite side, making sure folds meet at center of zipper. If using continuous zipper tape, attach zipper pull to tape.
Center the zipper strip over back of cushion top, beginning and ending on sides about 1 1/2” beyond corners; clip once into zipper strip seam allowance at each corner, and pivot.
Align center of boxing strip to front center of cushion top, matching print, if necessary; pin-mark pieces separately. Smooth boxing strip to right front corner; mark with 3/8” clip into seam allowance. Smooth boxing strip along right side of cushion top; pin boxing strip to cushion top about 6” from back corner.
Stitch boxing strip to cushion top, beginning at side pin and sewing 1/2” seam. For welted cushion, use welting foot or zipper foot. Match clip mark to front corner; pivot stitching at corner.
Continue stitching boxing strip to cushion top, matching center marks. Clip once into boxing strip seam allowance at left front corner; pivot. Stop stitching about 6” from back left corner.
Cut boxing strip 4” beyond point where it overlaps zipper pull end of zipper strip. Pin end of boxing strip to end of zipper strip, right sides together, matching all cut edges.
Stitch together 2” from end; pivot at zipper tape. Stitch along outer edge of zipper tape to within 1/2” of end; pivot. Place small scrap of fabric over zipper teeth. Stitch slowly across teeth to opposite side of zipper tape, taking care not to break needle; pivot. Stitch along opposite side of zipper tape until 2” from end; pivot, and stitch to edge.
Finger-press seam allowance toward boxing strip; finish sewing zipper strip and boxing strip to the cushion top. Small pocket forms to hide zipper pull when closed.
Cut opposite end of boxing strip 1” beyond point where it overlaps end of zipper strip. Pin ends together. Stitch 1/2” from ends, placing scrap of fabric over the zipper teeth and stitching slowly. Turn seam allowance toward boxing strip; finish sewing zipper strip and boxing strip to cushion top.
Fold boxing strip straight across at corner; mark opposite side of boxing strip with 3/8” clip into seam allowance. Repeat for all corners.
Open zipper partially. Pin boxing strip to the cushion bottom, matching clip marks to corners. Stitch. Turn right side out through zipper opening.
Yeah. All cushions finished for my Living Room Slipcover!