Spread some butter on the baguette, then layer each half with 1/2 wedge of Brie and 3 slices of prosciutto. If I remember, I like to leave the Brie out in the morning while I make breakfast, so it gets a bit soft which will make it easier to spread on the bread. If you don’t have time for that, take a knife, cut the wedge of brie into smaller bits and then place those on the bread.