ok well look lets take it from the point of view of something simply , lets say latext2html
https://slackbuilds.org/repository/1...ic/latex2html/
you will see source and slackbuild. Download the slackbuild. latext2html.tar.gz
right click on it, open with arc , extract to say desktop and you get a directory .
Now download the source and put it in the directory called latex2html. So now inside that directory you should have the source file (latex2html-2019.2.tar.gz) , readme, slack-desc,info, manual and the slackbuild file latex2html.Slackbuild; its the last file we will be interested in now.
First go to command line; log in as root eg $su ->pasword
# chmod a+x latex2html.SlackBuild
# ./latex2html.SlackBuild
after that last command you will see compile process and if lucky get a notification package in /tmp/package
to install # installpkg /tmp/packagename