Hello Dion,

thanks for reaching out to us.

This can be done by settings work hours a bit differently. Im not sure how many employees you currently have, but you need to make a new one specifically for this service. Since service duration and employee work hours are affecting the timeslots, we need to make sure that we set them up correctly.

Let's say that you have a Service A with a duration of 4 hours. You make a new Employee A and assign Service A to that Employee. This Employee will work only on this service because if you assign all services to this employee, and you try to set the work hours for other services, as well, you will see that there is no option to select work hours because it's overlapping. In other words, an Employee cant work on two services at the same time.

It's also important to set the Buffer Time After to 30 minutes. In this way, Amelia calculates the buffer time together with the service duration. In general settings, you need to make sure that the "Use service duration for booking a time slot" and "Include service buffer time in time slots" options are enabled.

When you set the Buffer Time and Service Duration, you need to set the Work Hours in Employee Settings.

If we follow your specific scenario, Work Hours should be set as per the screenshot below

When you go to the booking form, select the Service A, you will see that the timeslots are set to the duration and range you specified.

See the screenshot below - 

Please, let me know if it works or if you need assistance with anything else.