Folding instructions for the simple envelope with attached flap:Here's a diagram for the simple envelope. The dotted lines represent score lines. Cut on the red lines.
It should look similar to this when you're done cutting.
Valley fold all remaining score lines. Use a bone folder or creasing tool for crisp folds.
Use a corner rounder to round the corners if desired.
Add white liner (double sided tape) to the left and right sides of the inside of the bottom flap.
Glue the tabs to the bottom of the envelope as shown.
Fold the side flaps in.
Fold the bottom flap up adhering it to the side flaps.
All done. Now you have the perfect sized envelope for your card.
The Folding instructions are the same for the envelope with the separate large flap except that you will need to glue the top flap to the envelope before folding.