Add chuck roast, quartered onion, garlic cloves, bay leaves, avocado leaves (optional), peppercorns, oregano, and salt to a large stock pot. Cover with 8-10 cups of water, bring to a boil, then cover and simmer for 3 hours or until tender and easy to shred. Add more water, as needed.
Shred beef with two forks and add to a bowl. Strain beef broth through a fine-mesh strainer and set aside until needed. Discard solids. Submerge corn husks in warm water for at least 30 minutes.
Remove stems and seeds from dried chiles, then toast in a hot cast-iron skillet until aromatic. Tear or cut into smaller pieces, then add to a jar and cover with 3 cups of hot broth. Seal the jar until the chiles soften. When the broth is no longer hot, blend until smooth (I used an immersion blender), then strain for a silky texture.
Melt 1 tablespoon of lard in a large pan or Dutch oven, then saute 2 cups of chile sauce for a few minutes, over medium heat. Stir in shredded beef. If the mixture is too dry, add beef broth (but set aside at least 3 cups of broth for the masa).
Meanwhile, whip lard in a stand mixer using the whisk attachment until light, fluffy, and white, about 5 minutes.
In a large bowl, whisk masa harina, salt, baking powder, garlic powder, onion powder, and cumin until combined. With the mixer on low, alternate adding the masa mixture, 3 cups beef broth, and 1 cup chile sauce, a little at a time, until all the ingredients are combined. Switch to a paddle attachment, and continue mixing on medium until light and fluffy, and a pinch of the masa mixture floats in a cup of water.
Remove corn husks from water and give them a good shake, then pat dry. Lay them out on your work surface with the smooth side facing up and the narrow end pointing away from you. Spoon about 2 tablespoons of masa onto the wider end of each husk, spreading it out while leaving about a ½ to 1-inch border along the edges. Add 1 to 2 tablespoons of filling right down the center.
Fold one side of the husk over the filling, then bring the other side across to seal it. Fold the bottom end up toward the center, then tear a thin strip from another husk and tie it around the tamale to hold everything in place. Continue assembling until all the filling is used up.
Fill a pot with a steamer basket with a few cups of water; the water level should be below the bottom of the steamer basket. Arrange approximately 20 tamales, filling-side up. Pile extra corn husks on top. Bring to a boil, then lower the heat and steam, covered, for one hour. Let stand for 15 minutes before serving.
Notes
If you can't get the masa to float, don't worry, your tamales will still be delicious!
Overlap smaller husks to make them big enough to fill. The amount of dough and filling will vary depending on the size of the corn husk.
Tear the husks that are too small or too wrinkled into strips for tying the tamales once they're wrapped.
Don't pack the tamales tightly; leave room for air circulation. If packed tightly, they will take longer to cook and cook unevenly.
If you have leftover filling, masa, or corn husks, you can freeze them and use them the next time you make tamales.
Store tamales in the refrigerator for up to a week, or freeze for longer storage.