Directions

1. Rub the pork roast all over with the chili powder and salt. Heat the oil in a large skillet over medium-high heat. Add the pork and cook, turning occasionally, until browned, about 5 minutes.
2. Transfer to a 3 1/2- to 5-quart slow cooker. Add 1/4 cup water and cover. Cook on LOW until the pork is fork-tender, 5 1/2 to 6 hours.
3. Transfer pork to a cutting board and let stand 10 minutes. Discard liquid in crockery insert. Slice pork crosswise into 16 thin slices, discarding string.
4. For each serving, place 2 pork slices in a roll. Top with about 3 tablespoons guacamole and 2 tomato slices. Cut in half crosswise and serve warm.
5. *Tip: If you desire to tie the roast, cotton kitchen twine (also called butcher's twine) is handy to have on hand for a number of chores, especially tying roasts to help them keep their shape during cooking. If you don't have it, use unwaxed and unflavored dental floss.