The following is a list of notes on building MATE on Slackware -current:

Sat Apr  9 02:17:03 UTC 2016
MATE developers have reorganized mate-themes tarballs upstream to provide
sources matching your GTK+3 libraries. You can simply change the VERSION
and download link if you use a different GTK+3 library.

Tue Jun 11 00:41:15 UTC 2013
Pat has rebuilt xdg-utils in Slackware 14.1 to properly support MATE DE, so
xdg-utils patch is no longer needed in Slackware -current, but running
these two commands as normal user are still needed to set caja as the
default handler:

xdg-mime default caja-folder-handler.desktop inode/directory
xdg-mime default caja-folder-handler.desktop application/x-directory

please make a backup of your $HOME/.local/share/applications/defaults.list
before executing the above commands