I was looking up what to do with used, padded envelopes, and also found a tutorial on how to make cardboard mailers from cereal boxes. Thank you Chana of Adventures in Fluff.
I decided to try making a mailer from a tissue box; easy-peasy. Here is a little tutorial. You can leave it plain, or pretty up your mailer with some fancy paper. Have fun!
Open both ends of the box
Then open the side seams
Cut off all side flaps except those on the bottom
Trim side flaps to 1″, cut angles on corners
Tuck in the 3 flaps, then fold bottom of box up. Cut away remainder of box along top folded edge
Turn box inside out and crease folds with bone folder or rolling pin. Tuck short flaps to inside, then seal short edges with packing tape.
Fold long narrow edge over to close. Once you add contents, you can tape this shut.
All ready to address and mail!
Add pretty paper if you want
Glue or tape a label to the front