In a 6 quart slow cooker. Place onion slices on the bottom of the stoneware insert.
In a large mixing bowl, toss chicken parts with olive oil, salt, paprika, pepper, and all of the garlic cloves. Pour into slow cooker, on top of the onion.
Do not add water.
Cover and cook on low for 6-8 hours, or on high for 4-6. The longer you cook chicken-on-the-bone, the more tender it will be. If you use drumsticks, the ones on the side will brown and may stick to the sides of the crock, burning a bit. If this bothers you, you can rearrange them with tongs an hour before serving.