in bowl, combine brown sugar, salt, paprika, pepper, thyme, coriander, mustard powder, fennel and garlic powder.
Score diamond pattern on fatty side of pork. Insert knife into pork to create 6 small pockets; insert 1 garlic clove in each.
Rub pork all over with 8 tablespoons spice mixture; reserve rest. Wrap pork with plastic; refrigerate overnight.
Preheat oven to 350 degrees. Remove plastic from pork; place fat side up, in oven-safe insert of slow cooker. Roast in oven for 45-60 minutes. Transfer insert to slow cooker base; add apple juice and water. Cover; cook on low, turning pork occasionally, 6-7 hours. Transfer pork to cutting board, reserving cooking liquid. Roughly chop meat with cleaver.
Place meat in bowl, allow to stand 5-10 minutes. Strain off any additional cooking liquid and add it to reserved cooking liquid. Ladle 1/2 to 3/4 cup of reserved liquid back over meat. Stir in 1-2 tablespoons spice mixture. Serve with rolls and BBQ sauce of your choice.