The flank steak is too big. Is it better to cut it and freeze it uncooked or to freeze the cooked leftovers?

Not sure if I am on the right track but I would cook the whole thing and then use the other half for beef and sesame noodle salad. This way the meat is ready and cool and would be perfect.

Good answers - thank you Nancy and Cynthia. I opted to freeze the uncooked portion with the intention of using it soon.

Either way....depends on your time now and estimated when you want to use the rest of the meat in future.
But if you cook all now and freeze some, you'll have more flexibilty in future.
With just a little defrosting, can then use the ready-cooked meat in stew, sandwiches, tacos, salad, etc.

You could do either, depending on what you want to do with the frozen portion. If you're planning a meal that requires starting from the very beginning, freeze it uncooked. On the other hand, if you freeze it after you've cooked it, you're halfway to a quick meal once it has thawed.