A flange is a decorative flap of material added to the body of the sewing project. It is most often used to add extra length and width to a decorative sofa or bed pillow, but a flange can be applied to the edges of bags, down the seam of any garment, or added to a quilt.
A flange adds visual width to any seam. It is decorative and adds interest to the body of the project. If used on a pillow, the flange can extend the width of the cushion on a couch or a bed so it covers from side to side. On a garment it does not necessarily need to stick out, but can be added along the seam line and then sewn down over the side of the seam to add detail to the garment.
If you are making an 45 cm (18 inch) pillow you can safely add an extra 5 to 7.5 cm (2 to 3 inches) around the body of the pillow to give it the look of a seam. You can use a different material on the face of the pillow and then the flange serves as a bordering frame. A smaller pillow needs a smaller flange so that the pillow and flange stay in proportion to one another.
Make a flange
Most of the time a flange is an extension of the fabric. It is the width of the project plus a few extra centimetres. For a 45 cm (18 inch) pillow, you would actually cut a 52.5 cm (21 inch) square and seam it all around three sides. Mark and stitch on the outside of the pillow square 7.5 cm (3 inches) inside that edge and put in a pillow insert. Stitch close to the insert on the open side and hand finish the outside seam.
Alternative flange look
Not all flanges are flat extensions; some can be ruffled. Make a ruffled flange by cutting the same material as the body of the project but cut the strip twice as wide as the finished flange and at least two-and-a-half times as long. Fold the flange in half, wrong sides together, and make a long running stitch along the raw edge. Gather into a ruffle. Pin the raw edge of the ruffled flange to the raw edge of one side of the pillow top and stitch in place. Finish the pillow by seaming three sides together and hand stitching the open side after the insert is in place. The ruffle becomes the flange.
Flange zipper position
Like many other pillows, putting a zipper in a flanged pillow will allow you to take the cover off and wash it. The zipper can be in the centre of the back of the pillow. Cut a 52.5 cm (21 inch) square for the front of the pillow and two 27.5 by 52.5 cm (11 by 21 inch) rectangles for the back. Seam the two rectangles and sew in the zipper on that seam. Finish the pillow as usual except that now the pillow insert will go in through the zipper seam and there is no handiwork required.