Follow these steps to make the rice ball that is under the fish in nigiri sushi.
First, dip both hands into a mixture of water and vinegar (the ratio should be 3 water to 1 vinegar)
With the fingers on your right hand, take about 20 grams of prepared sushi rice, and curl the fingers to form the rice into an oval shape. Set the molded rice down on the table to free your hands for the next step.
With the left fingers, pick up a piece of prepared fish, and smear a bit of wasabi in the centre with your right forefinger. Then, pick up the rice with your right hand and place it on the fish. Press the rice lightly down on the fish with your right forefinger.
Now here’s the important part:
Holding the sides of the sushi between your thumb and forefinger and with the fingers of your other hand underneath the rice, press the sides gently. Then, press the top with your right fingers and the end with your left thumb. Repeat the process by turning the fish around, so the other end can be shaped as well. You can repeat these steps if you feel the rice may fall apart.
The final shape of the nigiri sushi should look like an open fan if you look at it from the side. Also, if you insert a skewer through the middle of the molded rice, and hold it up, it shouldn’t fall apart or turn upside down.
It takes a lot of practice, but you’ll taste the difference when your rice is prepared well.
You’re now ready to eat the fruit of your labour.