UX for linking elements together

I'm looking for an intuitive way to let a user group elements together, a bit like Photoshop's 'Link Layers' - but preferably without popup menu.

Right now I'm thinking about the following:

The idea is that you can drag the elements to another group and they will be automatically linked. When you want to break the link you drag it to the bottom. No clue if people will get this - I still need to user test it.

But before I try that, I want to explore some alternatives. Are there any established standards for this or really well done examples in other programs or web apps?

I've seen a few answers below, but I think the most important difference is that there is no clear label for these groupings; it's more like linking.

End result

After @nightning's answer. Note that the labels on top are descriptions of the state of the group - not labels that uniquely identity the group.