Some of us TAC demos were discussing how to make envelopes from 8" x 8" paper (since TAC sells that size). Allison showed us her tutorial using a centering ruler, then I "revamped" it for using the Scor-Pal. I know there are sooooo many ways of making envelopes, this just happens to be my favorite.
I also really like using a piece of 12" x 12" paper, cut it down to 8" x 8" for the envelope, then use the scraps to make a matching card.
I've attached both the tutorial I made as well as a sample. Easy Peasy!