Measure and cut the main piece 19 inches wide by 13 inches tall (cut one), back pieces 12 inches wide by 13 inches tall (cut two 2), and ruffle piece 2.5” by 90” long.Take one of the 12″ by 13″ pieces and fold it over ½” on the 12″ side. Iron it in place.
Fold over the 12″ side another ½” and iron in place, hiding the raw edge inside. Repeat for the other 12” by 13” piece. Stitch the hems all the way down with a ⅜” seam.
Fold the ruffle in half, and stitch the two short ends together, so that you have a large loop of fabric. Use a serger or zigzag stitch to finish off the raw seam.
Create a narrow hem by pressing one raw edge over ¼” and then another ¼”. Stitch all the way around the ruffle piece. Put a gathering stitch in the unfinished side of the ruffle piece. Refer to the ruffle instructions here.
Sew the two back pieces to the front piece, with the ruffle sandwiched in between. Put the 19” by 13” main piece down with the right side of the fabric facing up.
Lay the two back pieces on the main front piece, with right sides together. Overlap the two back pieces, so that all the raw edges are lined up. The two hemmed sides of the back pieces should be in the middle.
Gently pull the gathering stitches on the ruffle piece until its length matches the diameter of the outside of the pillow cover. Sandwich the ruffle in between the front and back pieces, with the raw edge lined up with outside raw edges of the pillow cover pieces.
Make sure the back of the ruffle hem is facing the back pieces of the pillow cover, so that when you turn the pillow cover out, the hem will be facing the back.
Pin everything in place. Stitch all the way around the pillow cover with a ½” seam. Go around the pillow cover with a zigzag stitch to finish off the raw edges.
Turn the pillow cover right side out, making sure to push out the corners. Insert pillow or stuff with fluff.