I do most of my work these days just in my notes - writing self reflecting questions, planning, using the a lot question "if this will go wrong - what will be the reason?" (inverting the problem)
Once the notes are written, I manually extract a general product spec from it again in notes. Then I take the product spec to the LLM and it just implementes, quite quickly all the things that it might have taken me a week+ to think about.
Something that helps with planning is having the llm build mockup pages - just so that it will be easier for me to imagine and think how the solution might look like and what imporatnt, underlying factors or details i might have missed