This link shows how to snip the center cuts before you sew the two layers together. But in the demo I saw, the center cuts were made just a little differently.
http://beyondsockmonkeys.wordpress.c...s-2/tutorials/
Before you layer the two squares RST, cut the top square on the diagonal with your rotary cutter, but not all the way through the center. Make two slits on one diagonal, leaving the center of the square and the ends uncut. Then cut the other diagonal, making three cuts: a short one in the center and the two cuts like the first ones. By leaving some fabric together in the center, the square is less floppy, and is easier to handle. It is still quite easy to snip the rest of those diagonal lines after the square is sewn all around the outside.