Cut most of the fat off the roast and discard. To a small bowl, add the salt, smoked paprika, paprika, garlic powder, black pepper, coriander, Aleppo pepper, brown sugar, mustard seed, and espresso, if using. Stir together to combine. If using Dijon mustard, instead of mustard seed, evenly coat the meat in the mustard. Evenly cover the meat in the the rub.
Preheat the oven to 300° F.
Heat a Dutch oven or a cast iron with the olive oil. Place the meat fat side down in the pan and sear the meat. Turn over and sear the other side, and then the ends.
Set the meat fat side up in the pan. Pour ½ cup water at the bottom of the pan. This will keep the coating remnants from burning. Cover and roast for 4 hours. Uncover and baste with some of the juices.
Roast for another 1 ¼ - 2 ¼ hours, basting a few more times. Check for doneness using a fork to pull apart. The meat should pull apart easily and be very moist inside. You can also use a meat thermometer. The meat should come to 195 or so using an instant thermometer. It will continue to cook once removed from the oven.
Pull apart using two forks and removing any large fat chunks. Skim off some of the fat and pour the juices over the meat, if desired. Serve with Homemade or store bought BBQ sauce, gluten free if needed.