Jashank Jeremy wrote an article on using FreeBSD, ZFS, GPT, and UEFI, on a 64-bit system.
Apparently, the trick to is to use GRUB’s kFreeBSD mode. Full information here:
Hmm, WordPress imbeds the entire source file listing of a Git.Github URL. So I’m splitting this URL, you’ll have to combine it yourself:
Also check out the reply from Felix Khrohn on Jashank’s Twitter post, with an URL to alternative method by Ganael Laplanche.