Place enough whole limes into the vase to fill it approximately three-quarters full.
Slice two or three additional limes into ¼-inch thick slices with the utility knife.
Slide the sliced limes down into the vase between the whole limes and the outside edge of the vase so that the sliced limes are visible through the sides of the vase. Push the limes all the way down to the bottom of the vase with the end of the wooden spoon, if necessary. Work until the entire outer edge of the vase has sliced limes covering it.
Fill the vase with cool water.
Place the fresh flowers into the vase, using the whole limes to hold the stems of the flowers in place. Insert the stems between the limes to create an arrangement you like.