We have the ability to allow booking series of times within one appointment. The customer can now select on a single time and that should allow them to book for the entire series of times, that you have set up on your schedule (eg. the customer can select either of the available dates and that should book them for Dec 1 at 10 am , Dec 2 10 am and Dec 3 at 10am).
1. You may start by setting up a fixed time schedule, here are the steps:
https://help.flexbooker.com/en/articles/2003957-setting-up-a-fixed-time-schedule
2. Under the schedule page, you can select on advanced options against the schedule, which should show you a pop-up page and enable "must be booked together" option:
***Once this feature is on, another thing to remember would be the following:***
For recurring schedules, all of the sessions in a week will be booked together at once (i.e. if there is a session every Tuesday and Thursday then both will be booked at once but only in the week being booked)
For non-recurring schedules, then all the sessions must be booked together