This Google Hangout link can actually be used by the teacher at any time. You can use the same Hangout link for all your classes as you need to. You might want to include a text box with some information about when you will be available for each class.
How to create a google hangout link
To ensure you have a successful hangout experience with your colleagues and students Manaiakalani have created this slide deck that covers best practice for Google Hangout set up and online management. There are also quick 'how to's' for using Screencastify and Quicktime should you wish to make any rewindable recordings.
Here's an example of how you might like to have your google hangout link set up. It's a good idea to have this on the home page of your site right at the top. If you are using multiple sites for different classes you'll want to set up every home page with the most up to date info and your hangout link.
Meet link: Whaea Kerry's Hangout Link
Times Whaea Kerry will be available on this hangout:
Tuesday 11.00 - 12.00
Link for more details. This needs to be turned on in the school domain.