FreeBSD installer sets up GPT by default. However, I have some servers which have spent years (decades?) in a NOC. Constant temperature, constant humidity, and very, very clean electricity. Some of these are so old, they don't know what to do with GPT.
I think the FreeBSD people are so used to the modifications they need to make, the documentation is really not very clear for newbies (which I am, at least in regards to BSD), so I'll try to document it better here. These are just notes for the time being.
The symptoms are, you do a very nice, clean install, then the server fails to boot! The trick is, on older computers, manually create partition table using MBR. You can use the GUI installer for it (I don't have pretty pictures of it), or you can choose the command line.
This can also be manually accomplished, so I'm including some notes here, though I really don't use them anymore. These are not formatted very well; like I said, they are just incomplete notes.
Install simple MBR boot loader (boots active slice):
If it still doesn't work, you can boot from the install image, then drop to a command prompt. At that point, attempt the information in From The Command Prompt above.
No guarantees. I have not done this successfully yet!