One thing I have experienced and can pass on as advice- make sure your warmed up. What I mean by this is the first person you talk to the day of your interview should not be the person interviewing you. Wake up early, eat a good breakfast and start using your voice. I find my best fluency is when I am "warmed up", have spoken to multiple people/used the phone etc. I have already faced some fears and the anxiety has been faced and goes down. This will not only help with confidence (arguably much more important than fluency) but will also help with your fluency. Also, practicing in a way that emulates the interview could be very helpful as well! Go in with a mindset to openly stutter. Don't try to hide your stuttering. If you exude confidence, that will shine through, and your ability as a communicator is made up of much more than your speech! Good luck! We are rooting for you.