Sprinkle chicken with 1/2 teaspoon of salt and 1/8 teaspoon of black pepper.
Heat the oil in a large skillet over medium-high heat; add chicken and cook for 2 minutes per side or until browned.
Transfer to a slow cooker.
Add garlic to skillet and saute for 30 seconds, stirring constantly.
Add wine (or juice/vinegar), scraping up all of the browned bits from the bottom of the pan; cook for 30 seconds; pour over chicken in slow cooker; add tomato paste, crushed red pepper flakes and tomatoes.
Cover and cook on HIGH for 4 hours. Stir in remaining salt and pepper, olives, and parsley.