Just use a stream of consciousness technique and blat it down; in these days of computer-aided writing you can type it in directly and then swap, cut, insert, or just generally meddle it about much more easily than in the old typewriter days. Once you’ve got your introduction, development, denouement, and conclusion (which should evolve naturally) down you can now expand it; just make sure the seams can’t be seen. If you use a cloud backup service you can save older copies too, just in case you make a wreck of what you’ve already done. Once you’ve put the flesh on the bones, you go back and apply the lipstick, powder, and paint, and that’s it, job done.
Computerses. It works for bloody Zuckerberg. It can work for you too.
And don’t forget to blame the EU. Ursula on der Clouden.