It’s basically having website cookies completely isolated in the same profile. You can also create containers for each website automatically so they can’t talk to each other. If you like having multiple emails from the same provider open, you can do that without logging out or making a new Firefox profile, so it’s like having all your settings and add-ons with the website flexibility of another profile.

Firefox multi account containers and temporary containers

You can fine tune your process but the most basic is a funnel (I.e. V60, chemex, kalita) with a paper filter on top with grounds on it that you just pour hot water on top and wait for it to filter down. Coffee machines do all this but they generally produce worse coffee outside of shops because no one cleans them as often as they should

You can do the same with a manual coffee brewer though- just use less coffee and water