I think that the key to practicing for presentations is not only practicing the speaking aspect of it itself, but also trying your best to replicate the atmosphere of the presentation. Presenting to no one is obviously much less nerve wracking than to a group of people, and what triggers our stutters the most is usually nerves and general anxiety. Therefore, try either getting close friends and family together to be your audience for a run through of the presentation, or use your imagination to its greatest extent in order to visualize you as speaking in the atmosphere. Hope this helps!