One odd and rather annoying thing about Google Hangouts as a simple way to create hold a conference is the lack of a fixed URL, you can invite people you already know, but typically you want to hangout with users not already in your circles, or who have circled you (seriously, it seems a bit creepy adding everyone you have just met).
The solution is to use the Google Calendar … (honestly)
Create an event any time, typically “now”
Click the link that says “Add Video Call”
Click join video call (or copy hyperlink)