Blue tape wrapped completely around and sliced off at the edge works well. Also a few toothpicks glued into waste areas. The toothpicks are by far the most stable, as in your stack just won't shift while you cut. Some use Brads nailed in the waste area, but it is a bit harder to sand a brad off than it is a toothpick. For brads use something like an anvil surface to beat them flush or prevent them from exiting the rear of the stack. Usually the trouble area is the center of the stack, and if you can get toothpicks in a 'last cut' waste area in the center it will prevent any center expansion.
Terry