Coarsely ground beans are excellent for French press coffee. If the grounds are too fine, the coffee will be harsh and over-extracted, and tiny grinds will pass through the filter and spoil the entire pot. A coffee made with coarse-ground beans, on the other hand, will be balanced and sediment-free. Finding freshly ground beans or grinding your own coffee at home might be a pain, but it's worth it for great coffee in the end.