On iOS, you can quickly ditch the current FaceID/TouchID session, and require a passcode for the next unlock, by holding power and volume buttons simultaneously for several seconds until the "power off" screen appears.
1. Check your “Emergency SOS” settings. It is possible to set it so that holding down those buttons like that initiates a countdown to an emergency call. Depending on the exact settings this may also be accompanies after a few seconds with a loud alarm.
If you are trying to surreptitiously disable biometrics this might be irksome.
2. I think these procedures were different on earlier phones or iOS versions, so test it out.
3. It also works to click the power button rapidly 5 times. That too can be set in the “Emergency SOS” setting to trigger an emergency call so check that before using it.
it's kinda a fun trick when I'm showing people something on my phone and need to unlock it :)
https://www.androidcentral.com/apps-software/how-to-disable-...
This is perhaps off topic, but does this mean you put your phone in your pocket with the screen facing outward? I do the opposite, am I weird?
EDIT: I suppose maybe you meant when the phone was on a table or something