Today I finished an envelope style sofa pillow and pillow form. All you need is a sewing machine, 2 fat quarters, muslin, fiberfill and a small amount of upholstery thread or button thread for hand sewing the pillow form opening closed.
Cut 2 14 1/2 inch squares of muslin. Sew together with a 1/4 inch seam, leaving a 4-5 inch opening at the bottom. Trim the corners. Turn right side out. Stuff with fiberfill. I tend to overstuff as I like my pillows FAT. Hand sew the opening closed with upholstery thread or button thread.
From 1 fat quarter, cut a 14 1/2 inch square. From the second fat quarter cut 2 pieces measuring 10 inches by 14 1/2 inches. Iron 1/4 inch hem on one of the 14 1/2 wide ends. Then fold over about an inch and iron again. Sew the hems of the two shorter pieces.
Pin, with the right sides together and the two shorter pieces overlapping, and sew a 1/4 inch seam all the way around. Trim the corners. Turn right side out. Iron the pillow cover. Then sew 1/8 to 1/4 inch around the outside of the pillow cover all the way around. Insert the pillow form. Viola! Instant easy pillow.