From the "router" board. The picture shows the jig I use to make "arcs". I am making the Generic Benroy and it just uses "Arcs". The beauty of the design is in it's simplicity.
The router base is removed and inset into the MDF. The PIN sticks UP into the 2x2 and into the drilled hole. The 2x2 is clamped above the work surface and the router makes a PERFECT arc.
I use a SWITCHED local plugin (the Blue box), a 1/4" bit, 1/4" depth of cut and move from left to right.