Set aside two to three pieces of fruit that are roughly the same size.
Fill the vase to the rim with the remaining whole pieces of fruit. Don't pack them in, but be sure the vase is full.
Carefully fill the vase with cool water, right up to just below the mouth of the vase.
Use a sharp knife to thinly slice the pieces of fruit you set aside in Step 1, so that you have a pile of neat, round slices. Discard any slices that are torn or mangled during cutting.
Use the handle of a wooden spoon to push the slices of fruit into the vase against the inside edge of the glass. Work until the cut slices completely frame the vase, and you can no longer see any of the whole fruit in the middle.
Gently ease the flower stems into the center of the vase, where the fruit will secure them in place.