Majority of everyone’s stutter originates with breathing. When our diaphragm freezes it lowers the pressure below vocal chords making the vocal chords not vibrate as theyre supposed to. Because of the pressure the vocal chords become tighter. Now if its isolated vocal chord blocking as you’re saying then even the breathiness(speaking with the breath) of diaphragmatic breathing will help in reducing the tension in the vocal chords. A deep tone also helps by vocalizing the words till your chest vibrates and not your larynx. Although it sounds unnatural at first you can reduce your fear to the point that you can safely vocalize normally without blocks. All of this is in no way easy and requires a ton of practice tho