After installing the Mosfet for the Hotbed to the Anet A8, I noticed the sensor wires touched the heat sink, which is not good. The solution was a bracket for the 40mm fan, first to prevent the Mosfet's heat sink from damaging the wires and second to cool it down, a win-win situation.
This bracket is clipped onto the Mosfet board itself, no screw required. Just snap the 40mm fan to the bracket, make sure the label is pointing outward to indicate it pulls the air out of the heat sink and not blowing into it. Next is to wire the fan to the Mosfet's DC volt connections and it's done.
Btw, the double mosfet holder was downloaded from https://www.thingiverse.com/thing:2018906
Update 1: Add a new design that is a bit taller to fit Mosfet with large heat sink.