Place the brisket on a large skillet on the stovetop and sear for 5 minutes on each side to form a nice brown crust.
After searing make five deep slits in the meat. Insert bay leaves, garlic cloves, and peppercorns into the slits.
Place brisket, salt, pepper, and water in a slow cooker. Cook on low for 6 hours turning after 3 hours.
Remove the brisket and discard the bay leaves and peppercorns and shred the meat.
Once the meat is cooked and shredded, cut it into small bite-size pieces. Put the meat back into the brisket juices and allow the meat to soak up all the juices.
Warm corn tortillas on a comal (griddle) so they are pliable. Add some shredded brisket down the center of the tortillas. Roll the tortillas tightly and then add a toothpick to each to keep them rolled.
In a deep pan or deep fryer heat the oil over high heat until it is very hot. Carefully drop the flautas into the hot oil. Fry just long enough for the tortillas to get crispy and a light golden color. Turn over at least once using tongs and then drain upright on paper towels to allow excess oil to drain. Serve immediately with toppings.
Avocado and Tomatillo Salsa:
Preheat oven to broil. Roast the tomatillos, jalapeños peppers, and garlic on a foil-lined baking sheet until blackened all over, about 5 minutes. Flip them over and roast the other sides for an additional 4 to 5 minutes. Watch carefully to prevent the tomatillos from burning.
Place roasted peppers in a plastic bag, close the bag and allow the peppers to steam until the skins loosen, about 10 minutes.
While the peppers are cooling off, peel off skin from garlic and discard. After the peppers have steamed, peel skin off and discard.
Place in a blender the cooled tomatillos, roasted and peeled peppers, roasted garlic, avocados, cilantro, water, and salt. Blend until creamy.
In a blender combine whole tomatoes, onion, garlic cloves, oregano, salt, pepper, parsley, water, and puree until smooth.
Pour the mixture into a saucepan and bring to a boil, reduce heat, and simmer to keep warm.
For a shortcut, serve the flautas with store-bough red and green salsa.