Creating Sushi Balls is simple if you follow these steps carefully:

1. Prepare Sushi Rice: Rinse the sushi rice under cold water until the water runs clear. Drain well.
2. Cook Rice: In a saucepan, combine the sushi rice and water. Bring to a boil, then reduce heat to low, cover, and simmer for about 20 minutes, or until the rice is tender.
3. Make Sushi Vinegar: While the rice is cooking, combine rice vinegar, sugar, and salt in a small bowl. Microwave for about 30 seconds until the sugar dissolves.
4. Season Rice: Once the rice is cooked, transfer it to a large bowl. Pour the vinegar mixture over the hot rice and gently fold it in using a wooden spoon. Let it cool slightly.
5. Prepare Fillings: In a separate bowl, mix the diced fish with mayonnaise, sesame oil, and soy sauce. Add chopped green onions and stir to combine.
6. Shape Sushi Balls: Once the rice is cool enough to handle, wet your hands with water to prevent sticking. Take a small handful of rice and flatten it in your palm.
7. Add Fillings: Place a teaspoon of the fish mixture and a few pieces of avocado and cucumber in the center of the flattened rice.
8. Form Balls: Carefully fold the rice over the fillings and shape it into a ball, ensuring the filling is completely enclosed.
9. Repeat: Continue this process until all the rice and filling are used up.
10. Garnish: Sprinkle sesame seeds on top of each sushi ball and garnish with nori strips for added flavor.

These steps will guide you in creating these incredible Sushi Balls easily and effectively.