Official way to add files to a livecd with livemedia-creator

[Niene Rink]

Hello,
really sorry when this is not the right place for the question.

I want to add own files to the home of liveuser.

I read many tutorials and the last one notes, that you have to add this
in the %post nochroot section of the flatks file.

I am using a mock environment and add the specific files to the root of
my mock, than add the section with:

tar -xvf test.tar.gz -C $INSTALL_ROOT/home/liveuser/

also the comand:
setxkbmap -de

in the section does not work.

Than i recreate the iso, putting the stuff into the %post section, as
mentioned also in a blog, no effort.

So, my question:
Is it possible to add files to the lived userhome directory or to the
livecd filesystem?
If yes, what is the official or best way to do this?

thx and greetings from germany

Jörn Rink