An ice maker assembly includes an ice tray having an ice forming plate with a top surface, a bottom surface and upstanding edges around a perimeter of the ice forming plate. A containment wall extends upwardly around the perimeter of the ice forming plate. The containment wall has a slot extending along a lower portion of the containment wall. The slot receives the upstanding edges of the ice forming plate to form the ice tray. A fluid line is configured to dispense water onto the top surface of the ice forming plate. A mechanical oscillating mechanism is coupled to the ice tray. The oscillating mechanism begins to rotate the tray in a rocking cycle about a transverse axis of the ice forming plate after ice has started to form along the top surface.