Well, right away, but it will better if you can wait 12-24 hours. Even then you will see super fresh coffee emits so much natural carbon dioxide that water can't fully saturate it. So use a "full immersion" brew method if that is the case: French Press, Clever Dripper, perhaps an Aeropress. For pourover drip of super fresh coffee, pre-soak the grinds for a long time.