Here is an easy pattern for making your own envelopes for your 4” x 4” cards.
Start with a 9” by 5 1/8” piece of paper. With your scoring tool, score the long side ½” from each edge. Score the short edge 3 7/8” from the bottom, 4 1/8” from previous score line, and 1” from previous line. Cut away the ½” side flaps from the bottom and top, as well as triangles from the center as shown below.
After cutting away the excess paper your envelope should look like this…
Fold along the score lines and add adhesive to the flaps. Round the corners of the top flap if you like and there ya go, your very own handmade envelope.