Ufw (Uncomplicated Firewall) is program for managing a netfilter
firewall.  It provides a command line interface and aims to be
uncomplicated and easy to use.

Slackware's 'rc.init2' script has an entry for a 'rc.firewall' script
which is not a default included file in the distribution which we can
hook into to start UFW as early as we can in the boot process by
creating a symlink like so:

ln -s /etc/rc.d/rc.ufw /etc/rc.d/rc.firewall

Then ensure you've set the 'rc.ufw' script exec permissions with:

chmod 755 /etc/rc.d/rc.ufw

to start UFW at system startup.

Ufw comes with a number of common application profiles.  Create
additional application profiles under /etc/ufw/applications.d.
Each profile should contain a list of rules which include a title,
description, and port(s) or port range.

A custom application profile should look similar to this:

[Application]
title=Application title
description=A description for the application.
ports=137,138/udp|139,445/tcp

Where xx.xx.xx.xx is the IP address of an external host, enable this
application profile by executing the following as root:

# ufw allow from xx.xx.xx.xx app Application

For a nice GUI program to control UFW with, check out 'gui-ufw' as
well on SBo.
