Quoting fffftr

XFCE can be installed on the stock XO OS with yum. It's in the repository.

As for the error screen, you never would have seen it if you hadn't done things the hard way. This is what debbootstrap is for.

Well, he was doing this from Gentoo .. it's not quite as easy as just calling debootstrap unless your already working on an apt based system.

I do agree however that debootstrapping the installation disk is a much better approach. You'll save quite a bit of package bloat (and room) if you go from Ubuntu minimal up to a minimal desktop.

You'll also be able to script 90% of the work which makes subsequent installs that follow your example much easier