Here are the instructions to use GFS repository through slackpkg+

1. Download and install slackpkg+ package from http://slakfinder.org/slackpkg+/
2. If you plan on using slackpkg+ you will need to set the PKGS_PRIORITY=( gfs ) 
   to gnome so that any packages in this repository do not get overwritten by Slackware's packages. 
   Granted there is only 1 to 3 packages that would get overwritten. Those packages would be: gjs, 
   gtk4,and pango or libsoup3 ( if it is included within the repositories .)
   (* You may remove other repositories (except slackpkgplus) if you don't use it  *)
3. Add gfs repository information and match it with your Slackware and 
   GFS version, and your architecture
   Example:

   For Slackware 15.0 (64 bit) and GNOME 41.10:
   MIRRORPLUS['gfs']=https://slackware.uk/gfs/15.0/41.10/x86_64/
   MIRRORPLUS['gfs']=https://reddoglinux.ddns.net/linux/gnome/41.x/x86_64/

   For Slackware Current (64 bit) and GNOME 42.10:
   MIRRORPLUS['gfs']=https://slackware.uk/gfs/current/42.10/x86_64/
   MIRRORPLUS['gfs']=https://reddoglinux.ddns.net/linux/gnome/42.x/x86_64/

   For Slackware Current (64 bit) and GNOME 43.10:
   MIRRORPLUS['gfs']=https://slackware.uk/gfs/current/43.10/x86_64/
   MIRRORPLUS['gfs']=https://reddoglinux.ddns.net/linux/gnome/43.x/x86_64/

   For Slackware Current (64 bit) and GNOME 44.5:
   MIRRORPLUS['gfs']=https://slackware.uk/gfs/current/44.5/x86_64/
   MIRRORPLUS['gfs']=https://reddoglinux.ddns.net/linux/gnome/44.x/x86_64/

4. Run slackpkg update gpg && slackpkg update && slackpkg install gfs && slackpkg upgrade-all
5. You can start managing your GFS packages through slackpkg+