Step 1Prepare the rice first. Cook the rice with the measured 2 1/2 cups water, or cook according to the manufacturer's instructions.
Step 2Cut each sheet of nori in half, crosswise, to be used to wrap the onigiri. Or, if you want smaller strips, fold the sheet twice more to get 8 strips.
Step 3When the rice is cooked, divide it into eight equal parts. Make the onigiri while the rice is hot. Take one portion of rice and put it in a small teacup or bowl.
Step 4Fill and shape the onigiri: Moisten your hands with the salt water to keep the rice from sticking (if you like your onigiri saltier, moisten your hands in the water, then rub a pinch of salt on your palm and rub your hands together). Make an indentation in the rice, and fill it with a little of the filling. Cover the filling with rice and mold the rice using your hands: For a triangular shape, cup one hand to hold the rice ball. Press gently with your other hand to create the top corner of the triangle, using your index and middle fingers and thumb as a guide. Turn the ball and repeat 2 more times to give the onigiri 3 corners; it will be approximately 1 inch thick. The onigiri can also be round or oval in shape.
Step 5Repeat with the rest of the rice and fillings to form 8 onigiri.
Step 6Wrap the onigiri with nori and press some roasted sesame seeds on the rice. Serve immediately. If you don't plan to eat the onigiri right away, wrap them in plastic but do not refrigerate.