This mounting plate fits no-name 6in fans (feel free to test with other fans), has four m1.7 (probably up to m2) screw holes to fasten the chosen fan, and other four m1.7 holes to screw into a cupboard or other place you want to have ventilated. Also has a hole for passing through cables (like extension cords, ethernet, etc).
You can use the plate to roughly mark where you want a hole for a vent before cutting.
The author marked this model as their own original creation.