Slow Cooker Mexican Beef Adobo (Authentic!)

Ingredients

• 2 lbs lean beef chuck roast (I used a fully trimmed, lean chuck roast)
• 4 dried guajillo chili pepper
• 4 dried pasilla chile peppers
• 1 dried ancho chile pepper
• 1/3 cup white vinegar
• 3 garlic cloves
• 1 tsp black pepper
• 1/2 tsp cumin
• 1/2 tsp oregano
• 2 bay leaves
• 2 cups chicken broth (or boiling water)