If "Absolute Linux" is based on Slackware, then you should be able to install the comparable fluxbox slackware package directly on it. Check the xap/ directory on any slackware mirror. If you need the SlackBuild script, then check the source directory.
The SlackBuild scripts in slackware's source and on SlackBuilds.org should, theoretically, work on any Distro aside from the last line which runs 'makepkg' in the package tree at the end of compiling and moving the files. If Absolute Linux uses a different package manager, that's where you would want to run the final package command.
Fluxbox doesn't have many dependencies other than the xlibs. I'm not sure about openbox and awesome, but I would guess the same is true.