I was able to install FreeBSD on GCE in a very direct way, without the hurdles of Qemu, gcutil, and the FreeBSD installer. All are great tools, but I think my apporach is somewhat more suitable for GCE, or at least much simpler. Much of this is well-known practice for installing manually, with some fluff for managing it as a disk image, as well as the few odd networking requirements of GCE (MTU and netmask).

My basic approach is to:

Use my FreeBSD machine at home to build a self-hosting "rescue" disk image for GCE.
Start a temporary Linux machine in GCE from a provided image.
Copy my image from home to a raw block device.
Start a FreeBSD machine in GCE using that block device as the root.

Once bootstrapped, I used this "rescue" machine to turn up more machines, then shut down this machine. I kept this "rescue" disk image handy for future rescues and turn-ups. Naturally, this is the bare minimum; you'll still want to install gcutil and stuff once you have your space bootstrapped. Although I typically prefer ZFS, I used UFS here for a smaller memory footprint and because the data on this filesystem is not precious. Either GPT or legacy partitioning schemes work.

On your FreeBSD machine at home, create a disk image:

truncate -s 2G /tmp/rescue.img
mdconfig -a -t vnode -f /tmp/rescue.img

adjust below if it says other than md0

Partition it with gpart:

gpart create -s gpt /dev/md0
gpart add -s 222 -t freebsd-boot -l rescue-boot md0
gpart add -t freebsd-ufs -l rescue-root md0
gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 md0
newfs -U /dev/md0p2
mount /dev/md0p2 /mnt

OR partition it the legacy way:

fdisk -B -b /boot/boot0 /dev/md0
bsdlabel -w -B /dev/md0s1 
newfs -U /dev/md0s1a
mount /dev/md0s1a /mnt

Install the base OS:

tar -C /mnt -xpf base.txz
tar -C /mnt -xpf doc.txz
tar -C /mnt -xpf games.txz
tar -C /mnt -xpf kernel.txz
tar -C /mnt -xpf lib32.txz

add ports.txz and/or src.txz if you prefer

Configure stuff:

chroot /mnt csh
newaliases
passwd root
mkdir /root/.ssh
# paste in your key
cat > /root/.ssh/authorized_keys << EOF
EOF
# change da0p1 to da0s1a if old style partition tables
echo '/dev/da0p2 / ufs rw,noatime,suiddir 1 1' > /etc/fstab
echo -Dh > /boot.config
echo 'console="comconsole"' > /boot/loader.conf
cat > /etc/rc.conf << EOF
console="comconsole"
hostname="rescue"
ifconfig_vtnet0="DHCP"
ntpd_enable="YES"
ntpd_sync_on_start="YES"
sshd_enable="YES"
EOF
cat > /etc/ssh/sshd_config << EOF
PasswordAuthentication no
PermitRootLogin yes
UseDNS no
UsePAM no  # Otherwise PAM will allow password auth.
Subsystem sftp /usr/libexec/sftp-server
EOF
cat > /etc/ntp.conf << EOF
server 169.254.169.254 burst iburst
EOF
cat > /etc/dhclient.conf << EOF
interface "vtnet0" {
  supersede subnet-mask 255.255.0.0;
}
EOF
cat > /etc/rc.local << EOF
ifconfig vtnet0 mtu 1460
EOF
ln -s /usr/share/zoneinfo/UTC /etc/localtime
exit

Dismount the image:

umount /mnt
mdconfig -d -u md0

Start a Linux machine on GCE. If you'll be subsequently creating machines with ZFS, choose one with enough RAM.
Copy rescue.img to it. (Remember, it must be dismounted first.)
Create a blank disk for FreeBSD and attach it to your Linux machine. I suggest naming the disk Rescue.
cat rescue.img > /dev/sdb [assuming your FreeBSD disk is sdb]
Detach Rescue from your Linux machine.
Create a new machine with Rescue attached as root.

after allowing time for it to boot, you should be able to ssh in as root.
destroy the Linux machine to save expense, if desired.

Transfer the new setup image:

reate the MBR partitioning scheme & make it bootable by installing bootcode.

gpart create -s mbr da0
gpart bootcode -b /boot/mbr da0
# Create an MBR partition. FreeBSD calls these "slices". Set it active so the system will boot from it.
gpart add -t freebsd da0
gpart set -a active -i 1 da0

# Inside the FreeBSD slice, create a bsdlabel partitioning scheme. Bootcode is needed here also.
gpart create -s bsd da0s1
gpart bootcode -b /boot/boot da0s1

# Create the FreeBSD "partitions" inside the slice.
gpart add -t freebsd-ufs  -a 4k -s 2g   da0s1
gpart add -t freebsd-swap -a 4k -s 512m da0s1
gpart add -t freebsd-ufs  -a 4k -s 1g   da0s1
gpart add -t freebsd-ufs  -a 4k -s 256m da0s1
gpart add -t freebsd-ufs  -a 4k         da0s1

# Format and label the filesystems before they are mounted, enabling soft updates for better performance:

glabel label swap /dev/da0s1b
newfs -L rootfs -U /dev/da0s1a
newfs -L varfs  -U /dev/da0s1d
newfs -L tmpfs  -U /dev/da0s1e
newfs -L usrfs  -U /dev/da0s1f

See http://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/disks.html#SAFE-SOFTUPDATES
for more information on using soft updates on the root filesystem.
Restore data to the new filesystems:

mount /dev/da0s1a /mnt
gzcat root.dump.gz | (cd /mnt && restore -rf -)
umount /mnt
# Repeat for /var, /tmp, /usr.

modify /etc/fstab

# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/label/swap         none            swap    sw              0       0
/dev/ufs/rootfs         /               ufs     rw              1       1
/dev/ufs/tmpfs          /tmp            ufs     rw              2       2
/dev/ufs/usrfs          /usr            ufs     rw              2       2
/dev/ufs/varfs          /var            ufs     rw              2       2

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dch/freebsd_on_gce.md

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