I don't know about you dear readers, but I love making my own envelopes and using them. They are really quite simple to make.
I use a plain envelope, large or small that I like the shape of as a template. To start with open the envelope right out and then take some nice paper that you like, make sure its of thick enough quality if you plan to send it through the mail. Trace around the template and chosen paper and cut out, taking note of where the folds go.
I like to line my envelopes with thinner paper either plain or patterned, so trace and cut that as well, making the lining a bit smaller than the outside piece.
Glue the lining to the outside piece and then fold into the envelope shape. Use a white sticky label on the front of the envelope to write the address on. Then enjoy making as many as you like with different papers. Tip: old book pages make a nice vintage envelope.
Here is another one I made with different paper and a different sized envelope.
You can see the lining inside this photo, before I glued it together.
Two of my home made envelopes. I love Japanese design paper and use these a lot.