Place beef and garlic in a large pot. Cover with cold water and bring to a boil over high heat; reduce heat, cover, and simmer until beef is tender and shreds easily, about 3 1/2 hours.

Meanwhile, place corn husks in a large container and cover with warm water; soak, weighed down with an inverted plate and a heavy can, until soft and pliable, about 3 hours.

Toast ancho chiles in a cast iron skillet; cool, then remove stems and seeds. Crumble and grind in a clean coffee grinder or with a mortar and pestle.

Heat oil in a large skillet; stir in flour and allow to brown slightly. Pour in 1 cup beef broth and stir until smooth. Mix in ground chiles, garlic, oregano, cumin seeds, ground cumin, red pepper flakes, vinegar, and salt. Stir shredded beef into skillet and cover. Let simmer for 45 minutes.

Place lard and salt in a large mixing bowl; beat with an electric mixer on high speed until fluffy. Add masa harina and beat at low speed until well mixed. Pour in reserved cooking liquid, a little at a time, until mixture is the consistency of soft cookie dough.

Drain water from corn husks. One at a time, flatten out each husk. Spread masa mixture onto the husk and meat mixture down the middle. Roll up the corn husk and secure with butcher's twine.