Get it laser cut, google “laser cut duroid” and you will find a bunch of options.
The manufacture probably has guidance for PCB routing machines, but the ask the laser guys first.
Otherwise make a set of teeth like soft jaws. The teeth are .050” wide. Mount a strip on edge, mill down to the .020” dimension. Then run a tiny mill or routing bit between the teeth to do the .060”. Clean everything, slightly loosen and pick out with tweezers.