I firmly believe that all things made or given should come in a nice packaging that will make the recipient feel that you've put in a lot of care and thought onto the package. There have been many occasions wherein I'm writing a letter and I find that the crisp white envelope is just way too stiff-- especially if I'm writing to a friend. Which is why I thought I'd make use of excess gift wrappers (which are nearly gathering dust) and turn those into pretty letter envelopes.
1. Get your envelope template and stick it on cardboard
2. Trace the outline of the envelope onto the blank side of the wrapping paper
3. Cut along the lines.
4. Fold all the sides in.
5. Keep in mind that the only flap that you'll have to use double-sided tape or glue on is the bottom one. You might also want to stick tape on the topmost flap for sealing in your letter later on.
I used thin double-sided tape so I wouldn't need to cut out excess if the tape is too wide. I prefer using double-sided tape over glue or paste as those tend to clump together leaving tiny bumps on the surface.
Easy, right? Apart from excess wrapping paper, you can also use old newspapers or magazines.