I am also not 100% sure I understand your question. I think that you are saying you lay out the backing, and put the batting over it, then can't line up the top because the middle layer (i.e. the batting) is bigger than the backing so you can't see the edges. As someone stated, your backing fabric should be at least 2 or 3 inches larger than your top ON ALL SIDES. In this case, a bit more is better. when you quilt, the backing fabric can get taken up a bit. After you cut the backing, the batting should be cut an inch or so smaller than the backing (but still larger than the top), so when you lay your batting on the backing, you will see a half inch or so of the backing peeking out around the edges.