That’s the neat part, all you need is a big jar, 24 hours in the fridge and filter patiently… the filtering isn’t really slow but you usually make a bunch.
Ratio of coffee to water is really the only tweak you can make. I used to use a whole 14OZ bag at a time and I’m not sure how much water anymore… I just used the same large glass jar every time, so there was more eyeball than measure.
It’s a very forgiving method, you can leave it in for 48+ hours, but 24 is the minimum. Once you filter it it’s good in the fridge for a week.