Help. Create Available slots from one calendar to another

Has anyone created a shortcut to take only available slots in one calendar and mark it as available in another calendar? I keep starting it but am realizing it’s a project so hoping to reuse someone else’s work.

Q) how would you define an available slot?

Would it not be a lack of an event in a calendar? I’m just trying to figure out how you would want to mark something as available when typical calendar entries are marking not available statuses.

The reason for the latter simply being that time utilisation is finite and non-utilisation is infinite unless you are applying very specific boundaries - e.g. Next 24 hours at the time of running.