Documentation on OpenBSD's 3-process privsep model?

I'd appreciate some pointers to documentation or minimal examples of
the 3-process privilege separation model for OpenBSD's daemons.
Internet searches pointed to skeleton examples at
github.com/krwesterback/newd and github.com/krwesterback/newdctl, but
those repos are now dead and it's unclear how authoritative they were
in the first place.