According to this site, the EFI boot loader for FreeBSD has yet to be integrated into the FreeBSD binary releases. I haven't checked the status myself, though, so I can't be sure that the information is outdated.
It's not 100% clear from your description if you're doing a FreeBSD-only setup or if you're triple-booting with Windows and Ubuntu. If the latter, that could cause complications, since on a GPT disk, Windows will insist on booting in EFI mode. Switching between BIOS-mode and EFI-mode booting is usually a bit awkward; however, my rEFInd boot manager can simplify the task on some (but not all) computers. Basically, you'd install rEFInd and edit
refind.conf: Uncomment the
scanfor line and ensure that
hdbios is among its options. This will enable rEFInd to chain from a standard EFI-mode boot into the BIOS-mode FreeBSD boot loader.
Although using rEFInd in this way might work if you've got a FreeBSD-only system, a simpler solution may work: Using a GPT-unaware partitioning tool, set the "boot flag" (aka the "active flag") on the MBR's type-0xEE protective partition. Some EFIs refuse to start an OS in BIOS/CSM/legacy mode unless an MBR partition is marked as active, and this workaround will satisfy such EFIs. See my Web page on this topic for more information and some other suggestions, should this solution fail.