Trim flap from envelope at the open end.
With the opening of the envelope at the top, score in 1.5” from the right, left and bottom edges of the envelope.
Score from inside corner to the outer point of the bottom corner squares.
You can now decorate the front of your gift bag, staying inside the score lines (for the purpose of this tutorial I just doodled with pens, you can add dp panels, stamps etc).
Step 5 (Optional)
If desired, use decorative scissor or corner rounder to scallop the top of your gift bag.
Crease the score lines and open up the envelope into a bag, I put my hand inside and gently work with the creases to form the bottom, the bottom corner squares will form into a point on each side.
Apply adhesive to the flaps and stick to the bottom of the bag.
Step 8 At the moment the sides will be 'bulging' just gently push them in and crease the other way part of the way down.Step 8
Punch holes at the top of the bag for the ribbon.
Finish decorating the bag as you wish.
You can make the bags with any sized envelope and any size as long as you score the same amount at the bottom and sides. (I think you can make them with a normal envelope, just seal it down and cut the end off so it opens, just think you will get a few more lines, but don't take my word for it!)