I feel that flow state[1] is possible as long as you don't feel distracted into doing other things and you're needed to guide the LLM along every few seconds/minutes (someone mentioned a pair-programming type tool in this thread). For me that works if you have a good spec + workflow tool (assuming you're doing interactive coding and not kicking off long running coding jobs). I feel that a good test of a workflow tool is that it should offload all bookkeeping from you, leaving you to just read the generated code and think about design/architecture.

I built one such tool for myself: https://www.shipsmooth.net. You can use it to spec/plan out a piece of work, and then easily keep updating the spec/plan as you churn through its implementation. The tool assumes that you will pretty much end up changing the spec/plan during implementation, based on how it's going. In general, I don't see how it's possible to one-shot high quality code for custom use cases.

[1] Going by the definition of flow state here: https://en.wikipedia.org/wiki/Flow_(psychology): "fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity. In essence, flow is characterized by the complete absorption in what one does, and a resulting transformation in one's sense of time."