This pillow belongs to my father-in-law's dog. At one point he must have chewed a corner of it and my father-in-law attempted to repair it with the limited sewing knowledge that he had. Unfortunately it affected the way the filling distributed in the pillow. I decided to repair the damage and the original loft of the pillow by restoring the box corners on the three affected corners.
1. First I used my seam ripper to undo the make-do patch-up job my father in law did.
Press it. Then trim off the excess fabric and the damaged area to make the seams straight.
2. Then after sewing the sides together, leaving a hole to turn it right-side-out later, I followed a tutorial in the book by Martha Stewart: Martha Stewart's Encyclopedia of Sewing and Fabric Crafts for box corners.
a. With "bag" still inside out, open up one corner so that the bottom seam is aligned with the adjacent side seam. Pin along the seam to keep the alignment in place. (Seams should be pressed open). Mark a point 2½ inches from the corner point,then draw line perpendicular to the seam at that point.
b. Machine-stitch along the perpendicular line.
c. Then trim off the resulting corner and zigzag to keep from fraying.
3. I then finished up by re-inserting the pillow-form and blind-stitch the remaining opening closed.
Hurray! I did it, one down and four more to go. And though I know that I am submitting this outside of the 24-hour time period, I still finished the sewing project within the allotted time. I'm very pleased with my work.