Trying to make ATC sized samples of the different techniques as I do them, so I will have an album to help me remember all the cool stuff I have learned on SCS.
I always start with the known size of an ATC to figure this out. So it is 2.5 x 3.5, then on the double fold pocket, the paper needs to be twice as wide and twice as tall--so start with 5 x 7 paper then follow the directions for the regular double fold pocket card. I think I just guessed on how much to fold down on the top left side. I had made several full sized ones by that time and had a feel for it.