Most of my square cards are 6"x6". And i never can find an Envelope to fit my cards, so i made one. I know we have many tutorials on the web, but i just didn't understand them. So here is how i did. I used MS score board, if you don't have one you can use ruler and score tool. I have here on first Photo Paper12"x12" square. I put my 6"x6" card right in the middle of this page, and that's how i find out where to make my first score, make sure to have your page in this positions like on this Photo.
"Kisme T" by Rick St. Dennis. You can find it at Etsy Shop.