Cut steak into strips. Combine 1/4 cup flour, the salt and pepper; toss with steak strips to coat thoroughly. Add to crock pot with onion, garlic, and half of green pepper strips; stir. Combine tomatoes with beef base, soy sauce and Worcestershire sauce. Pour into crock pot, moistening meat well. Cover and cook on low for 8-10 hours.
One hour before serving, turn on high and stir in remaining green pepper strips.
If thickened gravy is desired, make a smooth paste of 3 Tablespooons flour and 3 Tablespoons water; stir into crock pot. Cover and cook until thickened. Serve gravy with pepper steak over fluffy rice.