I want to try the HST by cutting squares and sewing 1/4" around the whole outside and then cutting it into 4 pieces. But I don't know how big to make my squares. If they are 2 1/2" trianges I'm making, how big are the squares suppose to be? And how much do you add to the 2 1/2" to get the right size? I hope someone can help me figure this out. I really want to try it.