Sunnys Easy Slow Cooker Sauerbraten

Name: Sunny's Easy Slow Cooker Sauerbraten
Ingredients: One 3-pound beef rump roast; Kosher salt; 1 pound frozen chopped onions; 3/4 cup red wine vinegar; 2 tablespoons pickling spice blend; 1 tablespoon honey; 8 to 10 whole black peppercorns; 3 tablespoons all-purpose flour; 3 tablespoons vegetable oil; 1 cup red wine, whatever type you like; 1 pound boiled peeled small potatoes, for serving; Sunny's Simple Red Cabbage Kraut, recipe follows; 4 cups beer (your favorite beer, as long as it's not too chocolatey dark); 3/4 cup sugar; 3/4 cup apple cider vinegar; 2 teaspoons red pepper flakes; 1 teaspoon mesquite liquid smoke; 4 cloves garlic, grated on a rasp grater or finely minced; 4 whole black peppercorns; 1/2 cup thinly sliced Vidalia onions; 1 head red cabbage, thinly sliced