Okay, I know Firestarter isn't the most updated or well conceived firewall solution for Slackware and it's very obnoxious (maybe?) to install due to the dependency requirements of:
and a few other Gnome components you'd rather not want install unless you don't care and want to resolve dependencies, but Firestarter is fairly easy to use, set up, and it can work with imported scripts and such.
Anyways, I found this gem of a Slackbuild today, and it works very nicely and doesn't require anything else (it even edits in the rc.firestarter scripts handlers for rc.local and rc.local_shutdown scripts for you).
This package also don't just include the RC script for console based startup and shutdown but also the INIT files for desktop integration startup also.
(It also doesn't do that ANNOYING double instance at startup.)
To build the package download all the files in the directory, make the firestarter.SlackBuild file executable, and then run it. Simple.
Mind you this package hasn't been updated for some time even from the original provider, but it does work rather nicely and behaves with all the current and existing Slackware releases out and is better engineered for people needing a fast and easy firewall setup like beginners and new users that may be intimidated by other firewall solutions out there that can be difficult for beginners to use and configure. Plus, Firestarter as a Firewall is more geared towards the Home/Office User (I wouldn't recommend it for Server usage though).
It has a nice feature to even block the network, lock the firewall, or reopen the network at a click of the mouse, and can even auto-stop the network in the case of an emergency.
I won't say it's a better firewall than Shorewall, FWBuilder, etc. but it's still very useful none-the-less.
So, have fun, and enjoy.
Many thanks to Andrea Sciucca at www.slacky.it
for this slackbuild.