Zocdoc + slots configured manually


I’m following a tutorial to create an application similar to Zocdoc. I want exactly the same principle of searching based on criteria.

The only thing I want differently is that the slots should not be shown automatically day by day, but rather that the doctor can set slots (day + time) only when they have availability.
The slots are therefore to be configured manually whenever they have free time.
I wish they could set up slots in advance for the month. The slots should be specific.

Would you know how I can do this in addition to the Zocdoc tutorial?

Thank you.