Trim excess fat from meat. If necessary, cut meat to fit into 3-1/2 to 5 quart slow cooker. Brush soy sauce over meat.
On large piece of foil, sprinkle and combine anise seeds, fennel seeds, caraway seeds, dill seeds and celery seeds. Roll roast in seeds to coat evenly. Place meat in slow cooker. Pour broth and 1/3 cup of the apple juice around meat.
Cover and cook on low heat setting 9 to 11 hours or on high heat setting for 4-1/2 to 5-1/2 hours.
Transfer meat to serving platter; cover meat with foil to keep warm. Reserve cooking liquid.
For gravy, strain cooking liquid and skim fat. Transfer liquid to small saucepan.
In small bowl, whisk remaining 1/3 cup apple juice and cornstarch. Add to saucepan.
Cook and stir over medium heat until thickened and bubbly. Cook and stir for 2 minutes more.