Build packages from sources for Slackware with slackbuilds.org
Follow @ggarronIntroduction
From Wikipedia:
SlackBuilds.org is a community-supported project for acquiring SlackBuild script of extra software not included within Slackware. A SlackBuild build script contains the build instructions and a source download link for building a particular package for your system. This is identical to the way Slackware’s official packages are built and is meant to address possible incompatibilities with community created binary packages while sacrificing the portability of typical binary distribution.
Slackbuilds is the best option to install software in Slackware, software that is not in the official slackware repository.
How to use Slackbuilds.org
I will use htop to show you how to use slackbuilds.org
Go to slackbuilds.org
Using the search box, look for htop

Once you found it, download the htop slackbuid script
Download the htop source, following the link in the slackbuilds’ htop homepage.
Unpack the tarbal of the htop slackbuild htop, I will create an src folder in my home folder.
mkdir ~/src
Then in that folder unpack the htop slackbuild script.
tar xvzf htop.tar.gz
Go into the folder
cd htop
Copy the source tarbal in the htop folder
Run the executable script in the ~/src/htop folder.
You will now have the Slackware binary for htop in the /tmp folder, so install it with
sudo installpkg /tmp/[newly created binary]
That is it, you can follow these same steps to install any other package available in the slackbuilds.org repository.