Bring a large pot of water to a rolling boil. Add the chilies and boil for about 5 minutes. Drain, discarding all of the water. Transfer the chilies to a food processor or blender. Process until you get a thick but slightly chunky sauce. Add the salt and briefly pulse to mix in. Store in a glass jar in the refrigerator for up to 3 weeks, or spoon into an ice cube tray and stored in a freezer bag.