I prefer to slice Brussels sprouts by hand instead of using a food processor or mandolin because you can get them just thick enough that way, and I happen to love their just-firm-enough bite. To get long, thin slices that hold their natural shape, I slice them lengthwise. It's easy! Just trim the root so the sprout will stand on a work surface and slice down lengthwise. If you prefer, pick up store-bought sliced ones.