This is a good tip. There's no set up needed, though - it's on by default. The above works well for iPhones with Touch ID.

On iPhone X, clicking the right button 5 times disables Face ID, but also invokes Emergency Call which makes a loud noise. An alternative is to simultaneously hold down the right button and one of the volume buttons until the power-off screen is displayed (and haptic feedback is given). The power-off screen can be dismissed by pressing the right button again, so this procedure can be silently done without taking your phone out of your pocket.

Source: https://www.imore.com/how-quickly-disable-face-id-iphone-x

In case your hands are..well, tied, another alternative is saying “hey Siri, whose phone is this?” - pulls up your contact card and disables biometric unlock.