Check meat after six hours; it should be absolutely falling apart (use two forks to test.) If it's not falling apart, return to the oven for another hour.
Remove meat from pot and place on a cutting board or other work surface. Use two forks to shred meat, discarding large pieces of fat.
Strain as much of the fat off the top of the cooking liquid as you can and discard it. Return the shredded meat to the cooking liquid, and keep warm until ready to serve. (You can also refrigerate the meat and liquid separately, then remove hardened fat once it's cold. Then heat up the liquid on the stovetop and return the meat to the liquid to warm up.
Serve on warm flour tortillas. Top with shredded lettuce, diced tomatoes, grated cheese, avocado slices, salsa, and whatever else you'd like.
