You have to clip the whole sandwich (backing, batting and top) together, not just
the backing. But first you clip the backing nice and taught but without stretching.
Then you lay the batting, smooth everything down, add the top, smooth everything
down again. Then carefully remove one clip at a time holding the backing with one
hand so it doesn't slip back but don't pull too tight, then clip the three layers together.
I also prefer to thread baste. Takes a while but I think it's worth it. After it's basted
I can fold it and leave it for a while before quilting and it does no harm.