When you have all tamales ready, place them, again as vertically as you can, into the prepared steamer with the open end on top. If there is space left in the steamer, tuck in some corn husks, so the tamales won’t dance around. Cover with more corn husks, and steam covered with a lid for 50 minutes to an hour. You know the tamales are ready when they come easily free from the husks. They will still be moist, and as they are released from the husks, you will see the moisture, like when you remove good moist muffins from their paper baking cups.
Finished tamales will stay warm for about 2 hours in the steamer. They can be made ahead several days before and stored in refrigerator, well wrapped. They can also be frozen for months. In either case, reheat in a steamer. For refrigerated tamales, it will take about 20 minutes and about 45 minutes for frozen tamales.
Note: To make seasoned oil, in a medium saucepan, heat 1 cup vegetable oil over medium heat, add a thick slice of onion and 4 garlic cloves. Cook for 15 minutes until completely browned. Remove onion and garlic before using the oil.