Once you enable Google Assistant it will listen to you all the time, even when the screen is off. Now just speak Ok Google or Hey Google and it will start
How To Turn On Off GOOGLE VOICE ASSISTANT For Android Phone / Tablet
Google's call screening: How to use and customize it - 9to5Google
How to use OK Google when the screen is off – TechCult
How to Turn Off Google Assistant on Android Devices – TechCult
How to Disable Google Assistant on Android – TechCult
Nothing Phone 1 - How To Use Google Assistant On Lock Screen
Fix System UI has Stopped Black Screen on Android – TechCult
Tech Cult on LinkedIn: #googleplaygames #gamingrevolution #pcbeta
How to use OK Google when the screen is off – TechCult
Daylyy: A new social app for photo-sharing, Tech Cult posted on the topic
How to Turn ON Device Flashlight Using Google Assistant – TechCult
Hey Google while screen is off - Google Assistant Community