As weird as it sounds I find kicking a wall helps me get through blocks. If I sense a word coming up that I am going to stutter on I kick the wall at the beginning of the word and this usually helps. However, you have to find a balance in the strength you kick because the harder you kick the better it works but the louder the sound so it’s possible they hear. You could also try other forms of contact eg. Tapping your hand on a desk or something else. I just like using my feet since they aren’t occupied holding the phone