For a large project, the real human trick for you to do is to figure out how to partition it down to separate apps, so that individual LLMs can work on them separately, as if they were their own employees in separate departments.

You then ask LLMs to first write features for the individual apps (in Markdown), giving it some early competitive guidelines.

You then tell LLMs to read that features document, and then write an architectural specification document. Tell it to maybe add example data structures, algorithms, or user interface layouts. All in Markdown.

You then feed these two documents to individual LLMs to write the rest of the code, usually starting with the data models first, then the algorithms, then the user interface.

Again, the trick is to partition your project to individual apps. Also an app isn't the full app. It might just be a data schema, a single GUI window, a marketing plan, etc.

The other hard part is to integrate the apps back together at the top level if they interact with each other...