How can I change the default Nautilus Bookmarks?

So when I add a new user, I want them to have a nice set of Nautilus bookmarks pre-loaded.

If I look in:

~/.config/gtk-3.0/bookmarks

I see this:

...file:///home/myuserid/Documentsfile:///home/myuserid/Musicfile:///home/myuserid/Picturesfile:///home/myuserid/Videosfile:///home/myuserid/Downloads...

Simple enough but actually not very helpful. How does this file get created?