How to create a "Request group membership form"

How do you create the "Request group membership (form)"?

In my GroupType permissions, I selected the check box to allow an Outsider to "Request group membership (form)." This adds a "Request membership" button to the Group page.

Clicking on that button displays a page titled "Request membership for [name of group]" along with the "Request membership" button again. There is no other content on the page. Clicking on the button again results in a message that says "The membership was successfully edited." However, the user doesn't know he or she has not yet been added to the group and the group admin receives no email notification that a user has requested membership and has no information on which to make a decision.

I'm struggling with how to create the form that should link to the button. I was expecting the user to be able to click on the "Request membership" button and fill in a form with questions I create (like an application form). Then I think I can use rules to notify the user and group admin that a new membership request has been submitted.

I originally thought creating this form might be related to the Group Member Profile, but Outsiders don't have permission to use those profiles.

I can't find any instructions or link about how to create the "Request group membership (form)." Can someone who has had success with this explain how to do it?

Thanks!