Do this: right at the beginning of the presentation, find a word that you stutter on, and then do an easy, voluntary stutter on that word. For, example saying "Hi My name is L L L L Luke, while maintaining full eye contact and composure. Start by talking slow and by projecting your voice. Take pause to breathe frequently, and continue stuttering on purpose if you start getting anxious. This slowly brings down your anxiety level. How? because the audience now knows that you've a stutter, and you'll be relieved from the pressure of having to hide it. Some people disclose they've stutter before difficult presentations , and that seem to have similar effect of relieving the tension. For me, the previous approach works best for big presentations. DM me if you've more questions.