Cut Roast In Half; Place In Large Resealable Plastic Bag Or Glass Dish. In A Bowl, Combine The Water, Soy Sauce, Sesame Seeds, Molasses, Vinegar, Onions, Garlic Powder And Cayenne. Pour Half Over The Roast. Cover The Pork And Remaining Marinade; Refrigerate Overnight. Drain Pork, Discarding Marinade. Place Roast In A 5-Qt. Slow Cooker; Add The Reserved Marinade. Cover And Cook On High For 1 Hour. Reduce Temperature To Low; Cook 8-9 Hours Longer Or Until Meat Is Tender. Remove The Roast And Keep Warm. In A Saucepan, Combine Cornstarch And Cold Water Until Smooth; Stir In Cooking Juices. Bring To A Boil; Boil And Stir For 2 Minutes. Serve With The Roast.