To me thinking hard involved the following steps-

1. Take a pen and paper.

2. Write down what we know.

3. Write down where we want to go.

4. Write down our methods of moving forward.

5. Make changes to 2, using 4, and see if we are getting closer to 3. And course correct based on that.

I still do it a lot. LLM's act as assist. Not as a wholesale replacement.