I have a huge stock pot to steam the tamales in. I add enough water to sit below a rack that I place in the bottom. I layer the tamales so that the steam can easily get around each of them. See picture above. I let them steam for a few hours. I add water about every 30 minutes to make sure that my pot does not go dry.
These tamales reheat well the next day. For our family of six I usually make about 30 tamales.