Here is a picture of the back of the finished product. Remember when I found the custom order fabric samples for 25 cents each? Well, I was waiting for the perfect backing fabric that didn't cost too much. I found a chenille curtain panel for $5, and it was big enough to make the backs of all the pillows. I washed it first so it would pucker a little, and it is sooo soft.
So here is what I did. I already had the pillow forms -- I highly recommend feather pillows. I got mine at Ikea and they didn't cost that much. They were 20-inch squares, so I cut the fabric for the front of the cover in a 21 inch square (I use a 1/2 inch seam allowance, so that is 20" + 1/2" + 1/2+). I made a few pillow covers, so I took brown packing paper and made a pattern that I could use over and over.
For the fabric on the back, you need 2 pieces, and they need to overlap about 3 inches. So, the width of each piece will be half of the pillow size (10") + 3 inch overlap (3") + seam allowance on side hem (1/2") plus hem on other edge (1/2") = 14". The height of these pieces will be simply 21". To make it easier, cut it out as one big piece and then cut it in half, eg, cut a piece that is 28" wide and 21" high. Then cut it in half.
You need to hem one side of each of the backing pieces. Fold it under 1/4" and iron, then fold under another 1/4" and sew.
Next, pin the pieces together right sides together. First pin one of the backing pieces to the front, and then pin the other backing piece over that. Sew 1/2" around the entire pillow. Then to make the seam stronger, sew a zig zag stitch around the entire seam allowance. Clip the corners and turn inside-out. Done. Hope it made sense.