Layer all of the ingredients in order in a 6-quart slow cooker. Cover and cook on low for 2 hours. [NOTE: While I have made this multiple times without an issue, it seems that many people have experienced the ingredients burning. I would recommend stirring all of the ingredients together and checking on it and stirring every 30 minutes to avoid an issue.]
Remove the lid and stir to combine. If not all of the chocolate is melted, cover and cook for an additional 30 minutes on low.
Using a spoon or cookie scoop, scoop mounds of the clusters onto parchment-lined baking sheets. Allow to sit at room temperature until completely set, 1 to 2 hours. The clusters can be stored in an airtight container in the refrigerator for up to 1 month. They also freeze very well!