I write rants online. Have been doing so for years, maybe a decade or more... some of my rants are taken very well and some are rather disjointed, but when I focus on something that's on my mind and let the passion come out in the rant, it becomes something more than a rant. People who don't know me start getting curious.
I realized that if I ever got the confidence to do the same thing out loud, it'd be a power.
I'd recommend starting off by writing without the idea of an audience in mind. Just put your thoughts on paper that you want to get across, straightforward and, if necessary, well researched. Make something that would persuade you if you were the audience. Argue with yourself and tell yourself all the flaws in your own argument. Look down on it. Then incorporate ways to address those flaws like you're arguing with yourself.
It's a terrifying concept, but the fact that you've received very little guidance means that if you get it all wrong or go completely off the rails, that's on them, not you. You can use that wiggle room to your advantage; there's nothing to fear from not being able to adhere to their requirements if they won't give you any. It's a total mindfuck to work within such loose constraints, but it gives you a freedom to format it however you want, and hold it against them if they have issues with that format.
Whatever expectations you've been made aware of are the only expectations you need to conform to; there is zero reason to try to guess what else they're expecting because they have chosen not to share those expectations with you. So you can do whatever you want basically.
(It took me nearly 30 years to go from being frozen terrified in those situations from fear of letting someone down by not guessing what they secretly wanted to being obstinately literalist in terms of following guidelines, so believe me, there is zero shame in struggling with a poorly designed assignment/request/requirement. If you don't end up feeling up to it, that's not a personal failure because that also is on their inability to clarify.)