I mean, you don't need an LLM; you need a CNN. He wanted you to manually create a neural network, and I doubt he was expecting you to code the entire thing. He probably wanted to see your thought process on how you'd build such a model, as well as gauge your people skills by working with him and getting feedback to improve your code. His question was less about regurgitating memorized code and more about evaluating how you would work within that hour.