This is from Allrecipes.com, which is an excellent site for recipes:
3 cups water 1 teaspoon salt 1 teaspoon ground black pepper 1 teaspoon dried oregano 1 teaspoon dried basil 1 teaspoon onion salt 1 teaspoon dried parsley 1 teaspoon garlic powder 1 bay leaf 1 (.7 ounce) package dry Italian-style salad dressing mix 1 (5 pound) rump roast
Combine water with salt, ground black pepper, oregano, basil, onion salt, parsley, garlic powder, bay leaf, and salad dressing mix in a saucepan. Stir well, and bring to a boil.
Place roast in slow cooker, and pour salad dressing mixture over the meat.
Cover, and cook on Low for 10 to 12 hours, or on High for 4 to 5 hours. When done, remove bay leaf, and shred meat with a fork.