Both Microsoft and Google provide the technology to reserve calendar timeslots that can be easily seen and scheduled. These slots are useful when you don't know who needs to meet with you, but you want to make yourself available. For example, for weekly office hours, you can set up to a two-hour time slot that people can book in 30-minute intervals.
Google provides documentation that lists the steps to create reserved slots within G Suite.
Additional learning videos can be found in Virginia Tech's LinkedIn Learning site
Microsoft provides documentation that lists the steps to create reserved slots withing Microsoft 365 Bookings.