Bootstrapping usb flash

[Mikko Heiskanen]

I have a Lacie Orange 7Gb usb flash drive, into which I've tried to 
install
FreeBSD 6-RELEASE a couple of times.
I've had no luck booting it, only a "invalid diskslice" -message after 
normal
installation and boot.
However, netbsd3 boots nicely with default install off the drive,
as does archlinux after modifying the mkinitrd.conf a little.

I was wondering if there is something I could do to make FreeBSD boot 
off
it too, since it is the OS I would prefer.
TIA

ps. I'm not subscribed atm