You can get 16 LTCs from a 12x12 sheet of paper. You start by cutting the 12x12 into four 5x7s, then cut those into quarters. You'll be left with a small square scrap of paper in the middle of the original sheet. Link to a video showing how.

Template for cutting LTCs from a 12" x 12" cardstock: http://www.create-with-joy.com/2012/05/woyww-tips-for-making-atcs.html