How do I display most recent network posts without a plugin?

I'm wondering what the code would look like to query and get the most recent network posts without using a plugin? I need to add this loop to my index.php page and am trying to figure out how to do that. I've looked at the global posts feed and widget and unfortunately I'm not sure what I need to get this running. Can someone give a little direction on what that would look like? I assume this isn't the first time this is asked, so maybe I can be pointed in the right direction?

Thanks so much,