1/3 cup firmly packed light brown sugar
2 1/2 teaspoons salt
1 1/2 teaspoons garlic powder
1 1/2 teaspoons paprika
1 teaspoon onion powder
1/2 teaspoon ground red pepper
1 (4- to 5-lb.) bone-in pork shoulder roast (Boston butt)
1 cup yellow mustard
1/3 cup honey
1/4 cup apple cider vinegar
1 1/2 teaspoons Worcestershire sauce
Stir together the brown sugar, salt, garlic powder, paprika, onion powder, and red pepper; rub brown sugar mixture over roast; place roast in a lightly greased 6-qt. slow cooker.
Whisk together mustard, honey, vinegar, and Worcestershire sauce. Pour mixture over top of roast. Cover and cook on LOW 8 to 10 hours (or on HIGH 4 to 6 hours) or until meat shreds easily with a fork. Let stand 15 minutes. Shred pork with a fork; stir until sauce is incorporated.