I have used the paper method and even ordered all sizes of the interfacing kind But then I discoverd El Burns method and now I can make any size perfect and no cost or paper to deal with.
Do watch her videos on useing squares to make 8 half sq triangles. So easy and you get perfect half sqs because you square them up. I never could get perfect ones when cut exact size, some would just not be right and some would stretch out of shape.