Disclaimer

Principles

The target directory is likely to be a SD card. 8G recommended.
Phase 1 populates the target directory with the main ARMedslack Linux distribution.
Phase 2 populates the target directory with parts from official Open Pandora OS and tweaked stuff.
A specific part of rc.local is executed during the first boot on a Pandora.
The files folder contains tweaked stuff.
The pkg folder contains pre-built packages from a previous alpha build.
The sources folder contains sources for essential programs.
Some proprietary stuff is missing, like 3D drivers.

Get the archive here.
If you don't run a Slackware or a derivative, get the Slackware's installpkg script here.
Put it in /sbin and make it executable.

You need to download the official Open Pandora rootfs: http://openpandora.org/firmware/pandora-rootfs.tar.bz2
Uncompress it as root anywhere and link it to the build directory as "pandora-rootfs".
Format a 8G or more SD card with the Ext2 filesystem. To make explanations clear, name it SLACK.
If you don't know how to format a drive, use GParted under Linux, or run their Live-CD. Here's the manual.
It's highly recommended to have a second partition formated as a swap. 256M or more is a good choice.

Run as su -.
For this very first alpha build, don't remove the SD card now, you have to edit ie.: /media/SLACK/etc/rc.d/rc.local

Remove simple-comments in order to produce the needed packages during the first boot.
Put the SD card in the Pandora, and power it on.
The Pandora will generate all (or almost all) needed packages.
The Pandora will power off after having done the job. May last for one hour or two.
Remove the card.
Save all /media/SLACK/tmp/*.t?z in the PHASE-1.sh

 MYPKGS="/mnt/hd/sdb4/stockage/pandora/armed-pack/sbopkg/Aaa-base/"

folder of the build system.

Plug the net.
Launch sbopkg as su -, load the vrac1 queue file, process it saying yes (Q) to options and wait. This is gonna be very long. I really mean very.
Do the same with vrac2 and vrac3.
Save all /tmp/*.t?z in the MYPKGS="/mnt/hd/sdb4/stockage/pandora/armed-pack/sbopkg/Aaa-vrac/" folder of the build system.
Be careful with disk space, you may fill the card. If so, save and erase all /tmp/*.t?z between queues processing.

Create a new rootfs, with PHASE-1.sh and PHASE-2.sh
Edit /media/SLACK/etc/rc.d/rc.local to build the remaining packages to put in $MYPKGS/AAA-base/
Put the SD card in the Pandora, and power it on.
The Pandora will generate final needed packages.
The Pandora will power off after having done the job. May last for one hour or two.
Remove the card.
Save all /media/SLACK/tmp/*.t?z in $MYPKGS/AAA-base/ folder of the build system.
Now, you can create a complete rootfs.

In the sources folder, you'll find some programs that aren't automatically generated by the build system.
I ship a light, but optimized version of mplayer. If you want a big bunch of new features, just compile it after having installed many dependencies from /extra.

I don't list those dependencies for now, because i do more useful things ^^.

Xmms may just needs libmikmod.
Qt3 is a bit long to build. It should be build before the big playlist. I will probably include it in the alpha building.

It may look a bit messy for now (and indeed, some part have to be cleaned), but it's versatile, as i intended from the start.
Depending on what you comment/uncomment, you can produce an alpha build, very minimal, or a full build.
Depending on what you edit, you can use it to port any *NIX to Open Pandora, and maintain your build very easily
The -current build system is under work and is not released yet.