Three things. One: After you fold the freezer paper back to add the next fabric, use the "Add-a-Quarter" ruler (or any other ruler) to cut off the extra fabric beyond the 1/4 inch seam allowance. Then when you add the next piece, you line it up with that edge of fabric: no need to trim again and less fabric wasted.
Two: You can take that piece of freezer paper off at the end and reuse it. Many times. A friend used hers twenty times. What a saving of paper! And time!
Three: When folding the freezer paper, lay a ruler on the line to be folded and use the back of a seam ripper to "score" it on the line. Some people use an index card or such to help with the folding, but scoring lightly with the back side of a seam ripper and a ruler is so much more accurate. Another time saver when using your paper many times = You don't have to score it again.