I didn't want to keep accumulating scraps from quilting projects (at a rapid rate) so I started using the scraps to make a strip to go down the back (usually from top to bottom) - I place the top and back together so the strip does not go down the center. I figure it is a win-win because I have less scraps to store and I use less fabric on the back because I have pieced that one strip - on my last quilt I was able to have one whole length of batik to use on another quilt instead of a bunch of smaller scraps.