The suggested /etc/rc.d/fossil at this page works well for me (I edited flags to suit my needs) except it would be better to have the line

rc_reload=NO

somewhere before the line

. /etc/rc.d/rc.subr

The effect of this change is that running rcctl reload fossil gives the error /etc/rc.d/fossil: reload is not supported instead of sending a SIGHUP to fossil, which seems to kill it.