Heat it in a water bath like some food is controllably heated -never be burned / never be hotter than boiling water. The water serves a heat buffer, equalizer and transfer / bridge with easy temperature control.

Take a large pan and fill it with partially with water. Place second pot / (cooking) vessel with a lid / ‘tupperware’ container with a lid with steam valve with the iOpen in it in the pan with the water. Heat the water to the temperature you like and keep it there until iOpen has heated up as well. Using the lid accelerates the heating. Do not let the water come to boil or bubble.

The temperature is easy to measure with what ever temperature gauge you have in the kitchen..