Get all results from within the hour

I'm trying to get all results within the hour. NOT THE PAST HOUR, but WITHIN THE HOUR.

For example, if it's currently 12:30, I want to get all results since 12:00, not 11:30. Or if it's 6:45, I want to get all results since 6:00, not 5:45.

How can I do this using Carbon and Laravel?

Here's what I've got so far:

$user = User::where('created_at', WHAT DO I PUT HERE)
    ->get();

via Chebli Mohamed