Podcasts and audiobook players have a sleep timer feature. There are many ways to express it. I prefer to have the least amount of taps. iBooks and Apple Podcasts can work with just 2 taps, while the Overcast app has a more customised popover interface and needs at least 3 taps or often more.

Podcasts app shows standard alert controller and Overcast shows popover.

Overcasts starts countdown as soon as you begin configuring the interval, this adds unnecessary pressure.