Answer: The device that cannot reliably deliver free-flow oxygen to the baby is the mask that is attached to self inflating bag. Some of the devices that can give free-flowing oxygen to the baby could be; a funnel, T-piece resuscitator, and tubing held in your hand that is up the baby's face.
The flow-inflating bag with a mask is what is needed to give free-flow oxygen, in replace of the mask attached to the self inflating bag.