To Exclude All Slots, you may refer to the diagram below.

Diagram 3.3.1 Steps on Excluding All Slots

As you can see, the excluded slots will be shown in black.

Diagram 3.3.2 Excluded Slots in Timetable Output

Note that, you need to exclude all slots before include preferred slot.

In Timetable Output, you may also be able to exclude other things such as

1. Exclude In the Slot: Exclude only a slot.
2. Exclude all in the Room: Exclude all the slots in the room chosen.
3. Exclude all in the Time Slot: Exclude all slots in the time slot chosen.
   
4. Exclude all in the day: Exclude all slots in the day chosen.