There are mainly three reasons why we make cutouts and slots in the PCB:
1. Structure and installation requirements;
2. To prevent the high-voltage components and near the low-voltage components on the PCB from being fired;
3. Adding the thermal pad by slotting, then it doesn’t need to consider electrical Safety requirements of electrical gap.
BTW, PCB slot design, whose processing of PCB file design is generally using Keep-Out layer or Mechanical layer.
