Cucumber rings are very common in garnishing. Go some creative with these slices and make other attractive look in shape of cucumber rings. See the picture tutorial for better understanding.
Things you Need
Cucumber
Knife
A round cutter (optional)
Method
Cut cucumber into thick slices.
Place cutter in center of cucumber or scoop out the center leaving a hollow in the middle.
Cucumber rings are ready for garnishing.
Picture Adopted from http://www.familyfreshmeals.com