Take a deep breath into your stomach/diaphragm, and then exhale. As you breath out, say three words e.g. cat mouse dog. Imagine your breath out like a wave and your words need to surf the wave. It’s about having momentum in your breathing so you don’t need to block. Blocking/stuttering nearly always involved getting “choked up”/having your air supply constricted so nothing comes out. You need to keep that channel open and speak with momentum from your exhalation.