Booking system for sport fiels

I am working on two apps and in both I would like to put a fixed slot booking system where users can book a field hour.
I am having difficulty because the calendar allows you to book variable hours and minutes and it is possible to book the same time several times. Has anyone worked on this before and can help?
Thank you


I think you need and mixture of these APP:


Maybe someone has already a whole system like you want and help you better otherwise, I might change my logic in one of my APPs and get your goal.

Note: this kind of APPs are not easy and there are several ways to develop them as you should know. You can have one working fine but using a backend very complex and difficult to maintain (scalability).