Since the metal surface of a motor driver unit can get very hot depending on how often it is used, anything touching it may be affected. Please install it out of the way, for example facing outward.
If you use double-sided tape to fix the unit in place, stick it to the case's resin part, keeping the serial number label and pressure vent clear.
The unit is waterproof, so it can be installed on the outside of the car. Make sure it is not exposed to rain, dust, gravel, etc.
Also, attach firmly so that it does not vibrate loose during driving and fall off. Check periodically that your securing agent (double-sided tape, cable ties, etc.) is still strong.