How do you best write one or multiple effective essays within the time constraints of an exam?

I believe that a common misconception exists among students taking exams for IB History (as well as related subjects) that it is best to allocate the entirety of the exam to just writing continuously. In my opinion, however, it is essential to spend at least a third of the time that it may take to write an essay to actually plan and outline it. It is in my experience incredibly challenging to produce an essay off the top of my head without having spent at least a bit of time thinking about how am going to write it. The advantage to not having to think about structuring your essay or recalling important points during writing is that you can write pretty much instinctively and at a very efficient pace. To illustrate my point, I can draw upon my own experience sitting my HL History Paper III. As I was given roughly 2.5 hours to produce 3 distinct essays, I spent roughly 30 minutes on planning (10 minutes per essay) and 90 minutes (30 minutes per essay) on writing, giving me ample to read over my work in the last few minutes as well. I admittedly ended up writing for a little longer than my planned 90 minutes, but I still ended up having enough time to outline my work in the beginning and review it at the end.During the planning session which I gave myself at the start of each HL History paper, I produced an outline for each essay in roughly the following format: 1-2 background/introductory facts or a relevant introductory quote, 1-2 relevant pieces of historiography to mention in the introductionrough, outline of a thesis/ overarching argument, 2-3 supporting arguments for each of my (usually 3) body paragraphs.