Rinse the sushi rice thoroughly under cold water until the water runs clear to remove excess starch.
In a rice cooker or a pot, combine the rinsed sushi rice and 2 1/2 cups of water. Let it soak for 30 minutes.
If using a rice cooker, turn it on and let the rice cook until it switches to the 'keep warm' function. If using a pot, bring to a boil, cover, and reduce the heat to low, cooking for about 18-20 minutes.
Once the rice is cooked, remove it from the heat and let it sit, covered, for 10 minutes.
In a small bowl, mix together salt, rice vinegar, and sugar, then microwave for 15 seconds until the sugar dissolves. Drizzle this mixture over the rice and gently fold it into the rice using a spatula to avoid making it mushy.
In another bowl, mix the shredded chicken with soy sauce and green onions until well combined.
Once the rice is cool enough to handle, wet your hands with water to prevent sticking. Take a small amount of rice (about 1/4 cup) and flatten it in your palm, leaving a small indentation in the center.
Place a spoonful of the chicken mixture into the indentation, then mold the rice around it to form a triangular or round shape. Press gently but firmly to ensure the onigiri holds its shape.
If desired, wrap a strip of nori around the base of the onigiri or sprinkle sesame seeds on top for added flavor and presentation.
Repeat the process until you have made all your onigiri.
Notes
Arrange the onigiri on a platter, garnished with fresh herbs or cucumber slices for color.