For the back, you need two pieces of fabric, making sure one of the sides overlaps the other by at least three inches. Making sure right sides are together, pin, and sew around the whole pillow.
Turn the pillow right side out. Put in your pillow. The fleece blanket I used had a blanket stitch around the outside. To save a step in sewing a seam, I cut the fabric for the flap of the envelope from the edge of the blanket to make use of this nicely sewn seam. I made these four pillow slip covers in about half an hour. Very simple and I love the festive look on my sofas. Stay tuned as I am going to be making some burlap pillows to dress up my sofas a little more.