Because it is almost impossible to predict what the most optimal shape af a part will be, depending on its loads and supports, the best way to design a part for topology optimization is to make it as solid as possible and let the particular algorithm decide where material should be removed. For the example of the stepper motor bracket, a solid part was designed, with cutouts for regions where there could be no material, because of other part interference, like the shaft coupling. Also, there was a cutout for the positioning and mounting of the bolts to secure the bracket.