Pat chicken breasts dry with paper towls and season with salt and pepper. In a large non-stick skillet over medium-high heat, heat oil until shimmery. Working in batches, brown chicken 3-4 minutes on each side until golden brown. Transfer seared chicken to a 4-qt slow cooker and set aside.
Saute onion, and garlic cloves in remaining pan drippings in skillet over medium-high heat until lightly golden and caramelized. Reduce heat to medium and stir in flour. Slowly whisk in wine and chicken broth until sauce is smooth. Bring sauce to a simmer over medium heat, stirring occasionally until thickened. Remove from heat and season with salt and pepper to taste.
Pour sauce over chicken in crockpot and sprinkle with thyme and parsley. Cook chicken on low heat 4-5 hours or until chicken is tender and registers 165F degrees on a thermometer.
Serve chicken and garlic sauce hot with pasta or rice. Enjoy!