Mix brown sugar, garlic powder, chili powder, paprika, oregano, onion powder, mustard seed, black pepper, cumin, coriander, and salt together in a small bowl.
Rub pork roast liberally with brown sugar mixture.
Heat oil in a large skillet over high heat. Add pork roast; cook until browned, 3 to 5 minutes per side.
Transfer pork to a slow cooker. Add water, liquid smoke, and chipotle peppers.
Cook on Low until pork is tender, about 6 hours. Transfer pork to a cutting board and pull apart with tongs.