How do I make one handed mode permanent?
On your device, open the Settings app. Search for One-handed mode. Turn on Use One-handed mode.
How do you use a big phone with one hand?
To enable this on most Android phones, go to Settings > System > Gestures > One-handed Mode and turn on the switch for Use one-handed mode. If you can't find the setting this way, go to Settings and search for that term.