This past fall I downgraded my cell phone from a smartphone to just a regular old cell phone. Partly because I was tired of paying the data fees when I didn't use enough data to make it worth it, and partly because I don't need the distraction of a smartphone. My new phone has a large touch screen, and I wanted to protect it, not to mention be able to find my phone quickly in the black hole that is my bag.
A few months later, I finally got around to making one. I briefly looked for a pattern but didn't find one, so I just played it by ear. My perfectionist tendencies almost got the better of me (when you wing it things don't usually work out perfectly), but I kept going and after about half an hour I called it good and threw it in my bag. And really, the more I see it, the more I love it. Sometimes I need to use things for a bit to realize how much I like them.
I have a bag of wool fabric scraps that I purchased at the NH Wool Arts Tour a few years ago (I've been making a braided rug with most of them). I found one wide enough to cover my phone and folded up the bottom edge, leaving enough fabric at the top for a flap, and sewed the sides together to form the base. Then I hemmed the edges and bottom of the flap.
My husband had told me that it was bad for wool to have direct contact with electronics, because of static electricity, so I knew I needed a lining. I had a packet of fabric squares from a 1930s fabric collection, so I sewed two together with the right sides facing, and hemmed the top edge. Then I carefully sewed the lining into the case by hand. It's slightly visible on the outside but not enough that it bothers me.
I picked out a button from my button jars, sewed it on, and snipped a slit large enough for the button. Even though it's wool and partially felted, I decided to blanket stitch around the opening to make it more secure. I couldn't find embroidery thread so I just used regular sewing thread. Lastly, I sewed on some felt flowers I bought a few years ago. It looks a little wonky but it does a great job, and I can always find my phone easily. Even though I got a little frustrated at times, sometimes just going for it and using what I have on hand is the best way to go.