Yi Jia Teow,
A simple way would be like; Adding a DS microflow as a data source for the Slots, As a result of the DS microflow, if the value is Day , then AM slot would be visible, otherway PM would be visible.
Instead of a DS microfow, you can of course use the values (Day, Night enum ) directly if it is reachable for the slots.
I hope this helps,
Ferhat