Currently, booking group appointments is not possible out of the box in Sesami. However, it is possible to create a workaround using multiple staff members.
To allow multiple bookings for the same service at the same time you will need multiple team members for the number of spaces available.
So for example, if you want to sell a service from 9am to 10am on a Monday and have six available booking spots, you will need to activate six team members with the same availability (in this instance, 9am to 10am on Monday) and this will allow customers to pick the time slot and register for six instances. After that it will be out of stock.