Tapping and pressing your watch face and buttons to control your watch isn’t always feasible. If you can’t use your other hand to navigate your watch, instead use your watch-wearing hand through gestures. To set this up, go to Settings > Accessibility > AssistiveTouch and turn on the switches for AssistiveTouch and Hand Gestures.
By default, pinching your thumb and forefinger moves forward to the next item on a screen or in a list, double-pinching your fingers moves to the previous item, clenching your hand activates or opens your current item, and double-clenching triggers an Action menu with an array of commands.