Create an ISO with different language settings

First i would like to say hi to everyone, that's my first post, so i thought a short hi is the least i should write =)

I found a great post from kcdtv but i had troubles to use the walkthrough to do the same with the newest kali live version.
Because i only use Kali booted from a usb drive (without persistence) and my keyboard is German-Swiss, every time i start up Kali first thing to do
is change the keyboard layout to German (Switzerland, no dead keys).
And that's how i found that post from 2014 on changing the layout of a custom build to spanish.
Now i was hoping someone here could help me with this.

Creating a Kali Live xfce still in english but changing the keyboard layout to de-ch.
Thanks to the detailed post from kcdtv a few pointers should be enough, i think=)