I would cut a strip of batting and sew it onto the quilt with the binding then turn both to the back making sure I tucked the batting inside the binding as I stitch the binding down. As a longarm quilter I usually trim the backing and the batting 1 inch from the edge of the top. I just think (and my customers like it) that it makes it easier to stitch the binding on. It also leaves plenty of batting to fill the binding. If the quilt is entered into a quilt show Judges will look to see if the binding is "filled". (At least in this area, it's important that the binding be full.)