I use this method a lot! I use the school glue method. I leave the backing all in one piece and mark the batting with a L and R after I cut the sides off - so I know how to reattach them. Put the L/R on both pieces of the batting where you cut the batting off. I do not quilt to the end of the batting - I leave around 4" on each side and pin on the edge so I don't go over the 4". This way there is enough room to attach the fusible interfacing that I use to put the batting back together. I have used the whipped stitching also, but prefer the fusible interfacing. I buy a yard, and cut it into 1" to 1 1/2" strips and just iron it on. I hope this makes sense. I roll up the edges of the loose piece of flimsy and backing to keep it out of the way, usually not a problem.