My previous mount failed (was 2mm thick) this is strong enough (5mm) to hold quite a lot of weight.
I used 4 M4x16 screws with washer to fix the mount in place to my robot base , and 4 M3x10 screws with washer to mount the motor.
Print with PETG 4 permiters 25% (or more) infill.
The author hasn't provided the model origin yet.