How to permanently assign a different keyboard layout to a USB keyboard?

How to permanently assign a different keyboard layout to a USB keyboard?

I often plugin a USB keyboard to my laptop (in addition to external
monitor and mouse, which all virtually convert my laptop to a desktop
computer) and I prefer using a different keyboard layout then.
I have to manually change the current keyboard layout each time I plugin
this USB keyboard.
And I'd like to use an automated way for this, if possible.
Radu's answer to the question here gives some clues, but it seems I'll
need a startup script for this task as the device ID for my USB keyboard
changes every time the computer starts.
This startup script will probably first include the command xinput -list |
grep "USB Keyboard", and another command to grab the first USB Keyboard ID
number displayed and then use it in the final command to set my chosen
layout for that USB keyboard as below:
setxkbmap -device <NUMBER> -layout <LAYOUT>