The fglrx driver has an integrated SlackBuild and can create a package out of it, if you specify it during the installation.
You can get it on the AMD website.
However, I wasn't pleased with the performance. I recommend using the latest Mesa open source drivers, they work much better for me (Radeon HD 6800) and are maintained by a small team of official developers from AMD.
![Smilie](https://www.linuxquestions.org/questions/images/smilies/smile.gif)
Just look at my signature for packages and SlackBuilds for the latest Mesa.