Once in a while I get a wrist watch as a present, and I don't like to wear them on the wrist.
Here is how I convert them into pocket watches. All you need is a strip of leather. A downside
of this method is that the crown remains on the side of the watch. The crown could potentially get stuck and be pulled out
while you take the "pocket watch" out of your pocket. However, it's not a problem with comfortable pants and large pockets.
Wrist watch to pocket watch conversion, front
Wrist watch to pocket watch conversion, back
You remove the wrist band and just loop a strip of leather through the watch band pins as shown above. Use a small hole punch to create holes for the chain or a suitable string. A few stitches on the back will keep the leather nicely folded.