If schedule lesson on demand, e.g. one to one tutorial or piano classes, where you will not set the schedule before hand, you could create lesson when issuing receipt.
In "Sale", Select the date and click on "Create Lesson"
Select the time, teachers and room. Click "Create 04/10" to create one date only, Create and Continue will create lesson on every weekday
starting from the start date. You will then see the timeslot and enroll as usual. The time slot will be created in the timetable when you submit.