With Online Booking system suggest a client to choose from ALL staff's available time. In that case client can choose any time from the list (for example 12:15 or 16:45). However, may appear free slots. 

Therefore, the system of the optimal time slots works by default. 

And you can set up Fixed booking Time.

 

Setting Fixed Time

Fixed Time add for each Staff individual in web-version dikidi.net/business.

For company: open Staff.

Open Staff's profile, click Online Booking and turn on "Fixed Time".

For Private specialist: 

Go to Settings > Online Booking > Settings.

Turn on Fixed Time

Select a type of fixed time:

• Start time of assignment by days of the week, if you want to fix the start time of online booking independent of particular date. 
• Assignment time for specific days, if you want to add or delete exact time ranges for online booking in particular dates.

 

Start time of assignment by days of the week

Select days, on which fixed time ranges are valid. Click "Add time".

In opened window select start time of assignment, which convenient for staff. Don't forget to save changes.

If you want to set up some days differently, click "+" and add settings.

 

Assignment time for specific days

Select Assignment time for specific days to set up the start time of online booking on particular dates.

Select Date in the calendar to set up Fixed Time. 

Note, that for assignment on particular dates can be select not only available, but also unavailable time!!!

For setting available time select date and click Add Time. Available Time should be active. Select time and click "Save"

For setting Unavailable Time for booking select Unavailable Time. Select unavailable time range for booking (or few time ranges) or make all day unavailable for booking. Click "Save" to add this time in your calendar.