Remove & discard chicken skin. Season chicken with garlic, thyme and salt.
Place chicken in slow cooker, pour oil & balsamic over. Cover and cook on low for 6-7 hours. Remove chicken from cooker, cover and keep warm. Discard juices.
In large bowl, toss greens, tomatoes, olives and feta; divide onto serving plates.
Slice chicken from the bone and top each salad with some.