Place beets in a 3-qt. slow cooker. Mix sugar, brown sugar, cornstarch and salt. Stir in orange juice and vinegar. Pour over beets; dot with butter.
Place cloves on a double thickness of cheesecloth. Gather corners of cloth to enclose seasonings; tie securely with string. Place bag in slow cooker. Cook, covered, on low until the beets are tender, 7-8 hours. Discard spice bag.