When you read a tutu pattern, this is what they mean when saying "cut 4 widths of" tulle at each length. Length is the "12 inches" and width is across the while 56" of the fabric. Then sew each of the 4 pieces end-to-end (short ends) to make a very, very long piece that is 12" by (56" * 4).
The base that all of the tulle/netting layers are sewn on to consists of two pieces -- the basque (top) and the panty, which are carefully fitted to each dancer and then sewn together. Note, the safety pins indicate where the lowest layer of tulle should be sewn.
The positioning for each layer is carefully measured and drawn. At the narrowest part (the front leg), ten tightly gathered layers must be sewn into a space of only about 2.5 - 3". Here you can see the 10th (bottom) layer is pinned on and ready to be sewn. After this, we pin and sew on the 1st (top) layer and continue working our way down, layer by layer.