In a medium bowl, combine soy sauce, brown sugar, olive oil, lime juice, ground allspice, ground cinnamon, ground nutmeg, dried thyme, smoked paprika, salt, black pepper, and cayenne pepper. Stir until the sugar is dissolved and the marinade is well mixed.
Add minced garlic, chopped onion, Scotch bonnet peppers, chopped scallions, and orange juice to the marinade. Mix well to combine all ingredients.
Place the chicken thighs in a large resealable plastic bag or a shallow dish. Pour the marinade over the chicken, ensuring all pieces are coated evenly. Seal the bag or cover the dish and refrigerate for at least 2 hours, preferably overnight for best flavor.
Transfer the marinated chicken thighs along with all the marinade into the slow cooker.
Cover and cook on low for 6 hours, or until the chicken is tender and cooked through (internal temperature should reach 165°F or 74°C).
Once cooked, carefully remove the chicken thighs from the slow cooker and place them on a serving platter.
Optional: To thicken the sauce, pour the cooking liquid into a small saucepan and simmer over medium heat for 5-10 minutes until slightly reduced. Spoon the sauce over the chicken before serving.
Serve the Slow Cooker Chicken Jerk hot with your favorite sides such as rice and peas or steamed vegetables.