As I have both the regular small cutters (that you may have seen elsewhere) and also the large cutters, I can efficiently use a whole carrot, with little more wastage than peeling carrots. Since I don't like waste, I usually eat the edges, if my little boy doesn't gobble them up! A mixture of large and small flowers is even more adorable, too.
Even if the carrot slice is slightly smaller than the cutter, it still works! Have a look at my Sweet and Sour Chicken below. Some of those flowers were cut from carrot slices that were slightly smaller than the diameter of the cutters. The inward points of the flower cutter still cut wedges in the edge of the carrot slice and they still have the cute flower appearance, in this case with certainly less wastage than peeling!