Mix garlic, rosemary, olive oil, wine, salt, pepper and 2 Tbsp. water in a 4- to 5-quart slow cooker. Mix well. Add chicken and turn each piece to coat well. Cover and cook on low until chicken is tender and cooked through, 3 to 4 hours.
Transfer chicken to a platter and tent loosely with foil. Remove 1/2 cup cooking liquid from slow cooker; place in a small bowl. Whisk in flour until no lumps remain. Pour flour mixture back into slow cooker and whisk until smooth. Turn heat to high and cook, uncovered and stirring occasionally, until thickened, about 15 minutes. Taste and adjust seasoning if necessary. Drizzle sauce over chicken and serve with rice, mashed potatoes or egg noodles, if desired.