In a small bowl combine all the ingredients for the rub. Mix until a thick paste forms.
Rub the paste all over the chicken, including under the skin. Set aside.
Place the celery, onions, and green onions in the bottom of the slow cooker.
Add in the tomato paste, chicken broth, and white wine. Mix well.
Place the chicken on top of the vegetables and cover. Cook on low for 6 hours.
Remove the chicken to a baking dish and broil for 5-10 minutes, 8 inches from heat, until the skin is crispy.
Meanwhile, add the flour to the vegetables and braising liquid in the slow cooker. Blend with an immersion blender until a gravy has formed.
Pour the gravy over top of the chicken and enjoy.