Let's assume that PkgBase is the way forward.
<https://alpha.pkgbase.live/> and so on.
In addition to the list, there's sometimes discussion of PkgBase in IRC for FreeBSD.
These are the instructions for pkgbase? https://wiki.freebsd.org/PkgBase just relate it to 12.0 releng, instead of head.
make [make flags] buildworld
make [make flags] buildkernel
# FreeBSD base system repository...