When you're opening up your schedule, you may want to restrict your clients to book in for a minimum amount of time. Rather than increase the slot service length, a more flexible way is to set up booking restrictions for staff members.
This won't force clients to book in one straight after the other, but rather force clients to choose from a set number of slots based on the booking restriction (but will adjust based on bookings). It will also only show the services that meet the minimum booking restriction time. Advantages of this are:
There are less unusable gaps in between bookings
It allows the flexibility that if a client books for a longer period than the booking restriction, the next available slots will automatically adjust. i.e. the booking restriction will apply to the remainder of the new available slots, but no extra gaps are introduced.
Example of booking restriction duration
This example assumes that services have a 15 minute post-booking buffer set up.
For Carrie J a booking restriction is set up for 2 hours, the schedule will show available booking slots every 2 hours and 15 minutes. The red box on the image show the slot that the minimum service will fit into, and the slot after it shows the post-booking buffer.
For Janet Plum a booking restriction is set up for 1 hour, the schedule will show available booking slots every 1 hours and 15 minutes.

If you have various post booking buffers lengths for services
Please note that this functionality will use the minimum post booking buffer out of all your services.
This means if you have various post booking buffers and have 15 mins for some services and 30 mins for others, the booking restriction will enforce 15 mins in its calculations.
If possible set all your post booking buffers consistent across all services to ensure the booking restriction minimises any gaps. If not then you may wish to switch this feature off and allow clients to book the various timeselots instead.
You can easily check the post booking buffers of all your services by navigating to Setup > Bookings > Services and look for the “P<mins>” (e.g. P30) next to each service.
Restricted services example
If a client wants to book Janet Plum, it will show the following services because they all meet her minimum booking restriction of 1 hour:

If a client wants to book Carrie J, it will show the following available service because only this one meets the minimum booking restriction of 2 hours (i.e. it will not show the 1 or 1.5 hour variations of this same service):

Automatic adjustment of available slot times if book longer service length
For Janet Plum, she initially had available booking times at 11.30am, 12.45pm and 2pm. If a client books a 1.5 hour service at 11.30am, you will see that the next available slot times have automatically adjusted down to maximise any future bookings, with the next timeslots now being at 1.15pm (was 12.45pm) and 2.30pm (was 2pm):

Setting up a booking restriction
Steps
Navigate to Setup > Accounts & Security > Staff & Admins (depending on what terminology has been set up)
Select the relevant staff member
Go to the Booking Restrictions section and select the desired restriction
Click Save

