You have a range of answers. In my last job, on my first day my manager asked if I would like to change the way I participate in a daily meeting. I thanked him for being flexible and turned down the offer. To get comfortable I needed be treated the same as everyone else and be given time to adapt. I have since managed a few people. I ask if there they have any particular needs or require specific support to accomplish their job. If you do something similar it will be up to the employee to inform you if there are any needs around their stutter. I personally am really open about my speech in my workplace. When I get ill my fluency drops off a cliff. I inform my manager if I get overwhelmed. Part of my role is presenting to different groups. They wanted me to present to a significant audience and I wasn’t comfortable doing that. I offered to work on presenting to bigger groups to get more comfortable. I wish my boss had requested I do this. It is important for progression and personal development to talk. I am sure when your new hire starts you will see how they settle, build that relationship and it should be obvious what help they do or don’t need.