Actually we just need the L bracket to make rings. I'll come back and use the bullseye next.
Put the cutter in the bracket and make the first cut.
Now the bottom is pretty grippy, but to be extra sure I clamped the bracket down gently to secure it well
I've also moved the blade out to make the bigger concentric cut. You will have to pick the cutter up off the paper to do this, so the L bracket is a must.