1. Find your favorite hat to use as a pattern, and an old shirt with a finished seam at the bottom.
(I am so picky, I have to have finished seams on everything!!)
(This is just an attempt at a close up of my old t-shirt)
3. Then sew around the wrong sides of the fabric and press the seam flat; trim the excess fabric. Then flip the hat and sew around the sides again to create a french seam. You don't have to use a french seam, you could just sew around once and be done. Then iron and wear.
I rolled the bottom of the hat up in this picture, you can't tell to much though.
Lastly enjoy your warm head!