One hand is a mountain range and the finger of the other hand is little Johnny jumping from moutain top to mountain top.
Put one hand out in front of you with your fingers splayed.
With the index finger of your other hand jump from finger tip to finger tip of your outstretched hand.
As you say Opps, make "Johnny" slide down the valley created between your outstretched index finger and thumb.
Then continue back again toward your little finger.