Take a normal sized French press (I’m using a Bodum Kenya 4 Cup Coffee maker)
Put in about half a packet of coffee (I’m using Tesco’s finest strongish coffee, because while good quality coffee is good, this takes half a packet per cafetière) (By half a packet, I mean about 110-120g, precision fans)
Stir it to make all the coffee wet.
Leave it for ten hours or so.
Filter it (For this, I plunge the french press, and then strain the remainder though a coffee filter. Which is, hilariously, the first time in around two decades I’ve used coffee filters for something not involving vodka)
Fridge the resulting coffee concentrate for a few hours, or until you’re ready to drink it.
In a glass, add a couple of ice cubes (If you feel enthusiastic, you can freeze some of the coffee into ice cubes and use those to not dilute the result) and enough coffee to cover them, a splash of simple syrup (sugar won’t dissolve) and another splash of milk or milk substitute (I like it with almond milk) to taste.