Trim: Trimming away excess bulk is always a great way to help the fabric lay smoothly. Grading the seam will disrupt a sharp under layer edge. Sew across the corner: The layers of the seam allowance need to fit into the inside of the corner. The smaller the corner the less room there is for the seam allowance. Rather than pivoting at the corner, sew across the corner for a couple of stitches. This makes “room” for the seam allowance.
The thicker the fabric, the more stitching across the corner that may be needed. Experiment with scraps of fabric to find what will work best for your fabric and interfacing combination.
Taper the corners: By tapering the seam line to take in the fabric at the corners you will create a more fitted cover and avoid the ears. Putting the cover on the pillow form inside out, allows you to mark the wrong side of the fabric as to where to start tapering the seam. A very gradual and slight taper is all that is usually needed to maintain a “normal” pillow shape.Sew across the corners: Just as when you sew a collar or cuff corner, stitching a few stitches across the corner allows room for the seam allowance and allows for a sharp corner.
Notching and clipping on inner and outer curved seams control the way the seam allowance overlaps and lays inside the item. Notching removes pieces of the seam allowance to prevent it from doubling up, laying on itself, or creating unwanted bulk. Clipping allows the seam allowance to spread and lay smoothly. Loosely woven fabric may require you to stagger the clipping and notching so that the seam is not weakened in one spot. Simply notch or clip one layer at a time and move over so that the layers of the seam allowance are not treated in the same spot. Clipping and notching in conjunction with grading the seam will help eliminate the abruptness of the seam allowance edge inside the garment. There are notions made specifically for turning out corners but a favorite is a “stuffing tool” that came in a bag of Polyfill many years ago. If that “tool” gets lost or broken, various sized dowels which are sharpened with a pencil sharpener work as well. Do not sharpen the dowels to a pencil-point sharpness; a dull pencil point on the end of the dowel works perfectly for turning out a corner. Having a variety of dowel sizes on hand is convenient for working with different weaves and weights of fabric as well as dealing with the variety of angles that make up corners on garments and home decorating items. Plain dowels are inexpensive, and since half the length of a dowel is more than sufficient for a turning tool, consider sharing the other half with a sewing friend. A bamboo skewer has a very sharp point but can be used by filing the point flat with an emery board or nail file.