A basic ring fence can be as simple as this:
I haven't watched the vid so I can't vouch for his technique, but they are safer than you'd imagine once you've got it and hands need not be near the cutters at all, at least with bigger joinery pieces such as he shows.
The "sweet spot" is on the ring, a filed nick, or a felt tip mark, positioned at the point where the ring is closest to the spindle and hence where deepest cut is possible. You guide the piece through as close to the mark as you can manage, having cautiously started it by letting it in from further back around the ring.
Modern ring fences tend to have more protection and guides than shown here.
Deema says oval - could be? they are generally circular but with the inner cut out off-centre to the outer edge