I always insist on hand stitching back covers using slipping thread despite the rather lengthy process! This is because not only does the finish have a traditional, tailored look but also it is 100% safe!. Metal grip, which is an alternative and quicker method of securing back covers, can wear through the fabric over the years. Slipping needles, which are curved, are easy to use and with careful placing of stitches, should ensure the seam is invisible! It is a bit of an art but my tip is to pin both fabrics together stretching the back cover fairly tightly, and always start the stitch a little above/behind the end point of the last stitch, so that when the thread is pulled the fabric sits flat producing an invisible seam.