Not sure what every one else does, but while I’m here will ask.
When i am on infinite flight, I’m always laid down, with my head on backrest.
I hold the phone perfectly straight and calibrate. Then look in settings to see if no matter how maybe times I move my phone, I can always get it back to 0% pitch instantly by eye, looking at the phone position as to the pitch display in settings. That’s how I know I’m set up and ready to go.
How do others do it? Calibrate mid flight or just before landing? I’m always in the same position physically when playing.