Originally Posted by May in Jersey

You said, "If I cut it into 3 pieces, and sew them together, it's too short, but there is excess on the sides."
so the backing is wide enough. What you can do is add a strip of another fabric between each of the 3 big wide pieces and the backing should be long enough.
wide piece #1
strip of another fabric
wide piece #2
strip of another fabric
wide piece #3