Download the SlackBuild archive of the application you wish to build and extract it in your build environment. For example, after extracting the chemtool.tar.gz archive, you should have the following directory tree:
Anonymous ftp access is available via ftp://ftp.slackbuilds.org if that's more convenient for you.
Next, download the source of the application from the address listed in the chemtool.info file and place it in the chemtool directory listed above. There is also a direct link to the source tarball on each application's page within our repository.
If your version of chemtool is newer than what is specified in the SlackBuild script, you will need to change the script accordingly. Using your preferred editor, open the chemtool.SlackBuild script and find the line which starts with "VERSION"
Change this line to reflect the current version of the chemtool source.
Make the script executable with chmod if necessary:
chmod +x chemtool.SlackBuild
Then run the script:
Note that for many builds, you will need to have a true login shell in order to have a correctly populated environment. Among other things, /usr/share/texmf/bin will not be in your PATH if you simply do "su" -- therefore, you will need to either use "su -l" when switching to root, or source the /etc/profile script after doing "su", or perhaps modifying /root/.bashrc to include necessary PATH elements.
Assuming everything happened according to plan (the compile finished without errors), the finished package should be in the directory declared as "OUTPUT" in the SlackBuild script (this defaults to the /tmp directory). Use installpkg to install it; you'll probably want to move it to some other location for safekeeping after it's installed.