The single hard drive in the Flybook shows up as /dev/hda in Linux. As per my requirements in the Disk Preparation section, I needed a large FAT32 volume for my data. The first partition with Windows had to remain, leaving the rest for Linux.

The original Windows C: drive (/dev/hda1) was 20 GB in size. With all my data files on /dev/hda2, I only needed the C: drive to contain the Windows OS and required applications. 20 GB was a waste of space so I used the Linux ntfsresize tool to shrink it down to 10 GB.
Even this is very generous - but I can revisit this when it's clear whether the Flybook can run Linux for everything except one or two essential Windows applications.

The Gentoo handbook recommends 3 partitions for Linux: boot, swap and root. All 3 appear to need to be primary partitions, but the existing Windows OS and my Data partition take up 2 primary partitions. The fdisk utility only allowed me to have 4 primary partitions on the disk, so I went with one swap partition and one main partition (i.e. have the boot mount on the same filesystem as the root).

The Flybook has 512MB of RAM, so I created a 1GB swap partition (/dev/hda3), and used the remainder for the root (/dev/hda4).
For filesystems, the ReiserFS sounded cool so I used that. I wanted a journaled filesystem as that's what I use on Mac OS X. Filesystem creation and mounting the new Flybook drives worked without problems.

Update: I knew I was missing something here with only 4 partitions allowed. Linux can actually boot off a logical partition within an extended partition. This means all necessary Linux partitions can be stored within one extended partition, removing the limitation of 4 primary partitions. So, for my requirements above, a more sensible solution would be: