In a pitcher, stir together water, salt and 1/2 teaspoon pepper, 1 teaspoon rosemary, 1 teaspoon thyme and 1 teaspoon oregano; whisk to combine.
Set aside. Place chicken into a large zip-top bag; pour reserved liquid mixture into the bag and seal. Place the bag into a large bowl and refrigerate for 12 to 24 hours.
When ready to cook, coat slow cooker with cooking spray. Drain and discard marinating liquid and place bird in crock. Rub the bird with olive oil and the remaining pepper, rosemary, thyme and oregano. Turn the bird breastside down in crock.
Cover and cook on LOW for 6 hours; check doneness. When done let the bird rest in the covered slow cooker for 10 minutes before serving.