Submerge the corn husks in a large bowl or sink filled with very hot water. Place a heavy plate on top to keep them submerged. Let them soak for at least 45 minutes until pliable.
Place the pork in a large pot and cover it with water. Bring to a boil, then reduce the heat and simmer until tender, about 1.5 to 2 hours. Ensure the pork reaches a safe internal temperature of 145°F (63°C) with a 3-minute rest, though it will need to be cooked much longer to shred easily.
Transfer the cooked pork to a cutting board to cool slightly, reserving 3 cups (710 ml) of the cooking liquid. Shred the pork into small pieces.
While the pork cooks, place the dried chiles in a separate pot and cover with water. Boil for 15 minutes until soft. Drain the chiles and place them in a blender with 5 cups (1.2 L) of fresh water, 2 teaspoons of salt, the minced garlic, and the oregano. Blend until smooth.
In a large pot, combine the shredded pork and the blended red chile sauce. Simmer over medium-low heat for 10 minutes, stirring frequently.
In a very large bowl, beat the lard or shortening with an electric mixer until fluffy. Add the masa, baking powder, and the remaining 5 teaspoons of salt. Mix well. Slowly knead in the reserved 3 cups (710 ml) of pork cooking liquid until the dough is light and creamy.
Take a soaked corn husk and pat it dry. Spread a 1/4-inch (6 mm) layer of masa over the wide end of the husk. Spoon about 1/4 cup of the pork mixture down the center of the masa.
Fold the long sides of the husk together so the masa encloses the filling. Fold the narrow, empty tail end of the husk up toward the center.
Fill a large steamer pot with enough water to reach just below the steamer basket. Arrange the tamales upright in the basket with the open ends facing up. Cover and steam over low heat for 1 to 1.5 hours, adding more water to the pot if needed, until the masa easily peels away from the husk.