What you need:
- The envelope you want to line
- Paper for lining
- Paper or cardboard for template
STEP 1: Measure your envelope. Subtract a few millimeters from each side, and keep in mind angles like the one above. You can let the liner stick half way down the envelope like I did, or line the whole thing. This isnt really necessary, and if your liner is expensive, this will cut the costs.
STEP 2: Make a template on sturdy paper or cardboard. Be more accurate than the drawing above suggests. (It´s not my actual template - I cheated a little bit)
STEP 3: Make sure your template fits the way you want inside your envelope. Here the sides are slightly more angled than the envelope, which you may or may not believe was done on purpose.
STEP 4: Cut as many liners as you need, with the help of your template and a good pair of scissors. You can also use a paper cutter if you have one.
STEP 5: Glue your liner to your envelope. To avoid wobbly paper, let it dry under a stack of books or something, to keep it nice and good looking.
Voilá! You have a pretty lined envelope!