I had a pen pal when I was a kid, and I always made my own envelopes out of old calendar pictures. I wanted to see if this would translate well into adulthood. Here's how it's done.
Like I said, I used to use old calendar photos. For this project I classed it up a bit using a black and white ad featured in W Magazine, but obviously you can use essentially any paper you want. Unfold an envelope of your choice and trace it onto the paper like this:
Then, fold and glue your new envelope together in the same way the envelope template was constructed.
As you can see from the photo above, I love plain, white note cards without lines. They're great for academic stuff, but I also love writing little notes and cards on them with a black pen.
Because my envelope was black, I addressed it with a silver pen. By the way, it's perfectly fine to send these through the mail; these envelopes would be a great excuse to send a good, old fashioned letter for no real reason at all. I hear people used to love that.
So I don't know, this might not be a grownup project but it's definitely fun for kids, and a good way to fake a decorative card last minute. Also, sorry for the poor quality photos, they were done on my iPhone. Let me know what you think!