I think the 5-layer seam is only needed if you're adding a front and back piece. If you already have the backing and batting on the quilt, you should be able to add flip and sew borders without her 5-layer seam, but you need to leave enough of the center un-quilted so that you have room to seam the border onto the center piece without the backing and batting in the way. Then flip the border over and finish quilting.
(Clear as mud?)