To stop mental chatter, you have to practice Void Meditation.
There are a couple of ways to achieve this, such as chanting mantras repetitively, focusing on an emotion, sound, color, or taste, focusing solely on the breath, or focusing on a tiny object, like in the Dot Meditation.
Mastering Void Meditation is the single most important way to clear the mind. This is one of the most fundamental and important skills to master as a Zevist.