The first thing I was told at my first pp class was pp will not save fabric. Measure your widest and longest part, add 1/2" and then cut that size rectangle. There is a ruler called Add Enough that is for paperpiecing, I have it but never figured it out. I prefer to overcut and get it done. I recommend Carol Doak's method to learn the basics. I took a Judy Niemeyer class and her way will tell you exact measurements but takes forever, hours of fussy prep work.