View the Smart Stack by turning the Digital Crown or swiping from the bottom of the screen. Touch and hold the screen to enter the edit mode. Tap the + button and scroll to the app you want to include (Timers, in this example). Tap a tile to add it to the stack; for Timers, there's a Set Timer 10 minutes option.

The Apple Watch SE 2 boasts a variety of health and safety features including a heart rate monitor, Fall Detection, and Crash Detection. It's also a great companion for active ind