In a small bowl, combine salt and ginger; rub over roast. Place in a deep glass bowl. In a large bowl, combine the water, vinegar and sugar. Pour half the marinade into a large saucepan; add half the onions, pickling spices, peppercorns, cloves and bay leaves. Bring to a boil. Pour over roast; turn to coat. Cover and refrigerate for 2 days, turning twice a day., To the remaining marinade, add the remaining onions, pickling spices, peppercorns, cloves and bay leaves. Cover and refrigerate., Drain roast, discarding marinade; pat roast dry. In a Dutch oven over medium-high heat, brown roast in oil on all sides. Pour 1 cup reserved marinade with all the onions and seasonings over roast (cover and refrigerate remaining marinade). Bring to a boil. Reduce heat; cover and simmer for 3 hours or until meat is tender., Strain cooking juices, discarding onions and seasonings. Add enough reserved marinade to the cooking juices to measure 3 cups. Pour into a large saucepan; bring to a boil. Add gingersnaps; reduce heat and simmer until gravy is thickened. Slice roast and serve with gravy.