Place a rack in the bottom of a steamer or large pot. Make sure that the rack is high enough to keep the tamales above the water. Place the tamales on the rack, folded side down, or if the pot is large enough, stand them up. Do not pack them tightly as they need to expand as they cook. Cover with addition husks or a towel to absorb the moisture. Bring the water to a boil, reduce to a gentle boil, and steam for an hour for each dozen tamales or until done. To test for doneness, open one end of the husk and if the masa pulls away from the wrapper, it is done.