Thomas has posted a step-by-step guide to achieving this over at his tech blog, Compute for Life, which you can check out in the source link. It is worth noting that Arch is running on top of the Android kennel. Essentially Thomas uses CyanogenMod and a few other Android apps to allow him to run Arch Linux off of the SD card.
He then uses a female-to-female USB adapter and a hub to connect a keyboard and mouse to the tablet. Touch support is not active yet, so the mouse and keyboard aspect is a requirement at this point.
source: Compute for Life via Hack-a-Day