Rinse chicken and pat dry. Cut across the grain into 1/4-inch-thick slices. In a bowl, mix garlic, cornstarch, soy sauce, oyster sauce, sugar, oil, fermented black beans, and salt until well blended. Add chicken and turn to coat. Cover and chill 30 minutes.
Meanwhile, in an 8- to 10-quart pan or a 14-inch wok, set a rack over at least 1 inch of water. Bring to a boil over high heat. Pour chicken and marinade into a shallow, rimmed pan or a heatproof dish that fits into the larger pan and place on rack. Cover the larger pan and steam until chicken slices are opaque in the center (cut to test), about 10 minutes.
Carefully lift pan with chicken off rack. Spoon chicken mixture onto plates and serve rice alongside.