This is amazing.
There a two different cuts of beef brisket, the first cut (or 'flat' cut) and the 2nd cut. The first cut is leaner and contains less fat. It slices beautifully. The 2nd cut, obviously, with more fat, will provide a flavorful sauce, as the roast slow cooks. We opt for the 1st cut, but lots of generations of home cooks have gone with the 2nd cut. Either one delivers amazing taste. As always, have your butcher trim away excess fat on the roast.