I've found that the instructions for how to build on FreeBSD are difficult to find. (They are located at the very bottom of the build-unix.md guide.)
In the beginning of the build-unix.md guide, there is a list for "BSD specific instructions" which has links to the build-netbsd.md and build-openbsd.md guides. I figured that the FreeBSD build instructions should be linked to as well in that list which would make them easier to discover.
(I also think the argument could be made to separate out the FreeBSD build instructions into a build-freebsd.md guide, which I'd be happy to do, but I'll leave that for discussion.)