Either use a cutting machine or cut the patterns out by hand.
Insert the antlers into the slots at the top.
Add a large cookie to the center (use a sheet of waxed paper if cookie is greasy) and fold flaps in to close. Use red label to secure flaps. If you used really thick cardstock, you may need to secure flaps with additional tape.
Tie a piece of baker's twine and gift tag around the envelope to finish.