Hi there and welcome to the Community, @Japa_Breathwork 
I am glad to say that our Appointment Booking app should work for this case!
If you’re not using the Google Calendar integration, the system won’t block slots automatically. This means a time slot will remain available no matter how many people book it, as there’s no way to set a booking limit in that setup.
However, with the Google Calendar integration enabled, only one booking per slot is available. If you’re going to connect your widget to the Google Calendar and let multiple users book the same slot, feel free to upvote this idea - Multiple appointments for the same time slot
Also. our Event Calendar might be a good option for this case, but, unfortunately, it doesn’t support the registration right in the widget. We already have this idea on the Wishlist and you can upvote it here - Register right in the widget.