This is my least favorite thing to do in quilting. I just recently started sandwiching a quilt 105 X 105, what a pain. In desperation I hung it on a wall and let gravity help, if the weather was better a clothsline would work. The layers are almost even at one end. That's where I start basting and work all the way to the other end. The backing and the batting are three or more inches larger than the top (safety zone). Then when I start quilting I work from the center. There are a lot of different ways to do this but this works for me. I envy the long armers more for their frames, that eliminate this step, then for their machines.