1. From the app admin page, go to Settings
2. Click General > find Time Slot
3. In Time slot type dropdown, select Flexible time slot (Allow overlapping)
4. Select Time stepping
5. Click Save

For example, the following product has
– Duration = 45 minutes
– Working hours: from 8 AM to 4 PM
– Time stepping = 15 minutes

=> Flexible time blocks will be interleaved: 8:00 AM – 8:45 AM; 8:15 AM – 9:00 AM; 8:30 AM – 9:15 AM; and so on.