After I measured out how much fabric I was going to need and cut out the rectangle, I turned the fabric inside out and sewed up two sides.
To sew the corner, rather than take the fabric out and cut the string, I simply raised the needle without detatching the fabric from the stitch, turned the fabric 90 degrees, and kept on going.
Now, I had an inside-out pillow case. I flipped the fabric back the right way and stuffed the pillow inside. Close up the remaining open side, and you have a beautiful, new pillow.
Since I already had the pillow and the fabric, this project didn't cost me anything! Something my husband and I both love!