My process is similar, but I recently added a new "critique the plan" feedback loop that is yielding good results. Steps:
1. Spec
2. Plan
3. Read the plan & tell it to fix its bad ideas.
4. (NB) Critique the plan (loop) & write a detailed report
5. Update the plan
6. Review and check the plan
7. Implement plan
Detailed here:
Same. In my experience, the first plan always benefits from being challenged once or twice by claude itself.