this repository is not maintained anymore. I used it years back when I still was using Funtoo-Linux. In the meanwhile I’ve switched to Arch linux and have a much better experience and do not have to wait minutes just for dependency resolution and hours for compilation.
Search for the config key overlay_defs in your /etc/layman/layman.cfg and
change uncomment it. Please note down the path that was given there (usually
/etc/layman/overlays).
curl -L https://github.com/NobbZ/gentoo-overlay/raw/master/repositories.xml > /etc/layman/overlays/nobbz.xml
layman -f -a NobbZ