Drill a hole in the end of a yardstick. Then saw off a few inches, and sandpaper or file rough edges + corners.
It's usually better to drill the stock while it's long, so there's something to hold/clamp. Short pieces have a tendency to spin with the drillbit. It's safer to drill the stick while it's long.
Now you have a convenient portable way to mount your phone-cam. Useful for hiking, or documenting instructables. The best camera, as they say, is the one with you.