What’s the easiest coffee brewing method?

It depends. If you have already have a coffee machine, you can just add coffee and room temperature water, and brew it. This will probably not going to yield the best coffee you can drink, so maybe looking at a similar approach could give you better tasting coffee. In order to do that you can add intermediate steps: grind your own coffee for freshness, measure the amount of coffee vs water for better ratio, and use better coffee paper filters.