I just put the flank steak in the crockpot in the morning - cover it with salsa and let it cook all day. A few hours before dinner (usually around 3 pm) I throw fresh string beans on top and let it cook until we eat, generally between 5 and 6. That's it and you've got a complete dinner!
I've also covered the flank steak with a mix of beef broth and onion soup mix (and liquid smoke if you can get it) instead of the salsa for more of a brisket type flavor.