In 5-quart Dutch oven, place round cooling rack. Pour boiling water in Dutch oven, almost touching rack. (Water should not touch tamales when they are added.) Place 6 empty tamale husks on top of rack. Stand tamales inside pots, leaning against sides all around. Cover; reduce heat to medium. Simmer gently 1 hour to 1 hour 15 minutes or until tamale dough becomes firm. Add more water if needed during cooking time. Let stand uncovered 10 to 15 minutes. Carefully unfold each tamale by removing string and opening husk.