One thing you could try is to write a full description of what you want to write about, explaining to yourself all the information you want to have included in high detail (in single, basic sentences, if needed), like a big list of facts.
I know some professional essayists that do it roughly that way, though it's an abridged version (I believe there's an extra step of making paragraphs) of the editorial process that has been used for writing for quite a while (usually with a team)
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You can even try a couple different orders, to see what format would work better
And then you can start glueing sentences together, and making it properly coherent