Denise Wild shows how easy it is to sew a knife-edge pillow.
A knife-edge pillow has straight edges and no zipper. First, cut two squares of fabric the same size as your pillow form. Next, mark the midway point along all four sides. Take a ruler and place it from corner to corner and mark ½'' in from the edge along that diagonal line. Repeat at all four corners. Use your French curve to mark form the ½'' corner point to the centre mark on your pillow. This softens the corners to prevent them from being too pointy. Repeat along all four sides. Now pin and sew around the pillow with a ½'' seam allowance, leaving an opening for inserting your pillow. Don't forget to backstitch at the beginning and end. Clip your corners and turn the fabric right-side out. Insert your pillow form and slip stitch the opening closed.