This article explains how to setup a traditional telephone conference call, where participants can call in to a specific number on their phone. Participants do not have to be on campus nor do they need an SNC email account.
Every event on a Google calendar includes the "Hangouts Meet" option, so start by scheduling a new event on your calendar for the date/time of your call. When you invite one or more people to your event, the Hangouts Meet option is turned on by default. If you have not invited anyone to your event, you can turn this option on manually by clicking the "Add conferencing" button while creating or editing the event:
After you have created and saved the event, click on the event while viewing your calendar. The event details will pop up, like this:
Notice that the above popup includes the "Join by phone" information. This shows you the telephone number for participants to call, along with the PIN they'll have to enter. That's it.
While you can invite all of your participants via the calendar, you can also just email everyone and give them the phone number and PIN. There is no cost to use this call-in feature.