I let my stutter disclose itself. The first time I block I'll just say something along the lines of "excuse me a moment, I have a speech impediment". I've never had an interviewer openly have any issues with it. And I've also been able to use it as a strength for a few questions. For example there's the common question of "tell me about a time you overcame a challenge" where I'd mention my struggle with my speech but not letting it hold me back.