The free pattern for a removable basic pillow form cover is a classic example. Although the directions call for a half-inch seam allowance, the cover is cut to the size of the form. This allows the entire cover to be filled with the pillow form. If the finished pillow is the same size as the pillow form, there is not enough pillow form to fill all the way out to the corners.
Seam-Trimming Method
Some fabrics will want to protrude even if they are firmly stuffed. In some cases, it is the seam allowances that are helping to cause the protruding corner. This is especially true when you are using heavy upholstery fabric. The simplest solution is to trim the seam allowance diagonally at the corners and the seam allowance as it approaches the corner before you add a seam finish. In some cases, this simple solution will eliminate the pointy corners.
A Sewing Method
A simple way to prevent protruding square corners on a pillow is to sew a couple of stitches across the corners which will round the corner ever so slightly. The number of stitches across the corner will be dictated by the weight of the fabric and the stitch length you are using. A piece of heavy upholstery fabric will require a few more stitches than a lightweight cotton fabric will need to prevent a poking corner. Trimming the seam allowances, as described in the previous step, before you add a seam finish also will contribute to eliminating the poking corners.
Tapering and Stitching Solution
If you’ve tried everything previously mentioned and the fabric still wants to protrude no matter what you do to tame it, there is another solution. By tapering the seams and sewing a few stitches across the corners, you take away fabric from the corners.
Press and Fold Solution
If trimming the seam allowance corner is not enough, you can tame the corner by sewing the corner with a couple of stitches across the corner.
Rounding Off Pillow Corners
Nothing says that you must have square corners on a pillow. You can round off the pillow corners without making an actually round pillow. This works especially well on a pillow that you are sewing with a piping or cording edge. In most cases, you will need to clip the cording’s seam allowance when you are sewing to allow the cording to smoothly go around the corner. The simplest template to round off a corner is a kitchen plate. Be sure to create the same round corner on all four corners by either folding the cover to cut all four corners at the same time or creating a paper template to repeat the corner on each corner of the pillow.
