Lockscreen

Hi there

You can set this here Go to Settings  > Display & Brightness > Auto-Lock, then choose a length of time.

Clicking the side button to lock your phone before putting it in your pocket is the right answer. The shortest auto-lock setting you can have is 30 seconds, which may be too long if you are having pocket dials.

You could just press the side button to put the phone in standby before sticking it in your pocket...