These are useful for letting other people automatically book themselves meetings with you, during certain "office hours" that you designate.

Making a slot

• calendar.google.com
• Create a new event and pick "Appointment Slots"
• Pick a slot size in minutes.
  

Letting people book appointments with you

• Share the link to the appointment page for this slot. With everyone whom you'd like to be able to book time with you.
  

Booking a slot

• Open the appointment page for the person you'd like to book time with. They shared a link with you.
• Click on an open slot, and book an appointment. This will auto-create a pre-accepted event in both your calendars.