You must click on the actual calendar itself and be in Day, Week, or 4 day view. NO! This creates an event, not an appointment. It might seem like you could create Appointment slots by clicking the red plus button. If you are in Month view (Press M) you will NOT be able to create Appointment slots. You want to be in Week view (press W) or Day view (Press D). Notice in the upper right next to the settings wheel is a drop down menu for the view.

You can not make appointment slots in regular personal Gmail.

If you are not finding appointment slots in the new Google Calendar it is because you’re on the wrong view… or you are in your Gmail. I created the slots of time on the calendar that I was available and the students clicked on the link and chose the spot that worked for them. I used Google Calendar Appointment slots to meet with students to review their student portfolios. In other words, instead of YOU manually adding each appointment to the calendar, people do it themselves. Appointment slots allow you to create available slots of people to sign up. So good news, appointment slots are still there for G Suite for Education users. It’s mostly just a new look not a loss of features. I’m really digging the new layout for Google Calendar. Make Appointment Slots in Google Calendar