@michaa7: pyfll is doumented enough - there are the configuration files for every iso in git. so one can checkout the repo and is nearly done with the configuration. Maybe some pathes or special memory settings, but it should work out of the box.
I would be glad if someone would write a Wiki entry - but wait - its done:
http://wiki.siduction.de/index.php?title=Erstellen_eines_siduction-%C3%A4hnlichen_ISOSure, there is room for improvement, but hey - its a wiki. Some additions: I don't see the need for a own partition - but why not. I've setup a debian mirror for our isos to speed up the build process a little bit - this may be a little bit of overkill for a home user, but hey - its really cool

- One need only approx 350 G for the repo in booth architectures and a internet connection that allows approx 5-15G daily download to maintain the mirror. I also setup the build dir in tmpfs - 5-8 G sould be sufficient, i take 20, because we share the buildplace with pbuilder.
There are three time consuming things within the build: 1. Downloading the needed packages (approx 1..3G, it depends), not that bad with a good connection, 2. unpack and configure the packages (nice, if one have enough Ram, one should use it), 3. Creating the squash filesystem (more and faster Processors are better, doing that in Ram is cool too).
On a normal PC with a good Internet connection a build should take approx 15-30 mins, we need 4-7 min on the buildserver, so one can add the time for downloading the finished iso. But the really timeconsuming thing is create/modify/debug a configuration, that can take some days.