Spray the bottom of the slow cooker with nonstick cooking spray.
Season the chicken with salt and pepper, then layer in the bottom of the slow cooker.
In a small bowl, combine garlic, thyme, balsamic vinegar, and orange juice.
Pour mixture over chicken. Cook on low for 4-6 hours or until chicken reaches 165 degrees on a food thermometer.
If desired, remove chicken from crock and pour remaining juices into small saucepan. Reduce the liquid by bringing to a rolling boil for 5-7 minutes, stirring occasionally.
Serve sauce over chicken.