Mexican Shredded Beef

3 lbs beef chuck roast
1 T cumin
1 T chili powder
1 t salt
1/2 t ground red pepper
1 cup salsa or picante
2 T water
1 T cornstarch
Taco shells

Combine spices and rub over roast. Place roast in slow cooker and cover with salsa. Cover, cook on low 8-10 hours. Remove roast from cooking liquid, trim fat and shred meat with two forks. Skim off fat from cooking liquid. Turn heat to high. Blend water and cornstarch in small bowl until smooth. Whisk into liquid in slow cooker. Cook, uncovered, 15 minutes or until thickened. Return beef to slow cooker. Cover, cook 15 minutes or until heated through. Adjust seasonings. Serve with taco shells.