Open Control Center
Swipe down from the top-right corner on iPhone with Face ID
Swipe up from the bottom edge on iPhone with a Home button
Tap the Focus button
Tap Do Not Disturb
Open Settings
Tap Focus
Tap Do Not Disturb
Turn on Do Not Disturb
Ask Siri to turn on Do Not Disturb
To turn it off, open Control Center and tap Do Not Disturb again