Zoom, Thinkific, Calendly, Doodle, Simply Book Me

Hello,

I have a thinkific website and they recommend  using a calendar service such as Calendly, Doodle or Simply Book Me and link it to zoom.  The problem is with these services they require a cut off point where attendees cannot book time into the class.  I want the class  to be a link that anyone enrolled can join at any time during the live class.

I want to be able to set up these classes without the booking requirement  of these calendar services and not have to set up each class one live link at time as thinkific is set up to do.

Am I missing something on these calendar services?  

I hope this makes sense