Do you have leftover batting scraps from all of your quilting projects?
Here's how I use up mine. This probably isn't the 'right' way to do things, but it works for me and I haven't had anyone return a quilt and say they had problems with it.
I take the strips of batting and overlap them by about 2 inches and then quilt a little closer than usual. If I need to add another piece, I just lay it in and keep on quilting. I've never had a problem with the batting shifting or getting a space in the quilt. I use poly batting most of the time so I don't know if this would work with cotton batting or not.
I have lots of leftover scraps and hope to use them up quickly!