I have a suggestion for you. I believe that a small change would broaden the scope of your plugin.
This is to allow the selection of multiple adjacent time slices at once. I wish to reserve a tennis court. I can decide to play for an hour, two or three hours, since there is no fixed time for the match. In the second case, I simultaneously selects and I pay all of a sudden two or three consecutive time slots.
I think it would a more flexible and broader use your plugin, free or paid version.
Thank you for your attention