Remove fat from meat. Cut meat to fit into a 3 1/2- to 4 1/2-quart slow cooker. Sprinkle meat with salt and pepper (optional). In a large skillet, cook meat in hot oil over medium heat until brown on all sides. Drain off fat. Place meat in cooker.
Combine in a small bowl the 1/2 cup water, Worcestershire sauce, tomato paste, garlic, and hot pepper sauce. Pour over meat in cooker.
Cover and cook on low-heat setting for 10 to 12 hours or on high-heat setting for 5 to 6 hours.
Transfer meat to serving platter, reserving cooking liquid. Cover meat with foil to keep warm.
For gravy, strain cooking liquid and skim fat. Transfer liquid to a medium saucepan.
In small bowl, combine cornstarch and the 1 tablespoon water, stir into liquid in saucepan. Cook and stir over medium heat until thickened and bubbly. Cook for an additional 2 minutes. Stir in horseradish and the 1/2 teaspoon salt. Serve gravy with meat.