There is always more than one way to skin a cat, so to speak!
Liz pins her quilts by pinning the backing to the carpet and then smoothing the next two layers down before pinning - man that is hard on the knees! Liz says it keeps her fit!
I layer my quilts by placing the newly ironed backing fabric with the right side (the printed side) face down on my kitchen table and then I slightly stretch it and tape it down all the way around it with masking tape. Isn't it lucky that my kitchen table is just a smidge less than 42" and is about 6 inches longer than it needs to be! YAY! It is so much easier to layer a quilt with a helper (sometimes my wonderful hubby, sometimes another Aussie Hero Friend) but I can do it alone. After the backing is is taped down firmly and there are NO wrinkles I lay down the batting. This has to be smoothed out really well too but this can be done by running your hands over it until it is sitting flat and again NO wrinkles. Finally the newly ironed quilt top goes down with the pretty side up. Once again it has to be smoothed down.
Most quilters pin the three layers together, some use a washable basting glue called "spray baste". I pin! A LOT! The more you pin the better chance you have that your quilt layers will not shift during the quilting process.