Place rice into a large bowl and cover with several inches of water. The water will become very cloudy right way. Drain this first batch of water immediately.

Cover the rice with water again. Use your hand to swirl the rice around for a few seconds, and then drain it again. Repeat this process until the water remains clear when you jostle the rice.

Drain the water once more and cover the rice by several inches with clean water. Let the rice soak for 30 minutes, then drain well in a fine-mesh sieve. Now the rice is ready to cook.

Place the rice, kombu if using, and water into the Instant Pot or a medium-sized nonreactive pot with a heavy bottom and a tight-fitting lid.

To cook in the Instant Pot: Position the lid, set the vent to sealing position, and cook on manual, high pressure for 5 minutes. Let the pressure release naturally for 10 minutes before carefully releasing any remaining pressure and opening the lid.

To cook on the stovetop: Position the lid, then turn heat to high and bring to a boil. When the water boils, lower the heat to low or medium-low (depending on your burner) to maintain a gentle simmer. Simmer until the water is absorbed, about 12 minutes. Then remove pot from the heat, leaving the lid closed, and let the rice steam for an additional 10 minutes.

While the rice cooks, stir together the vinegar, sugar, and salt in a small pot or microwave-safe bowl. Heat just until salt and sugar have dissolved.

Remove the kombu. Gently spoon cooked rice into a wide, shallow bowl. Pour vinegar mixture over rice.

Using a rice paddle or silicone spatula, gently cut and fold the rice to mix in the vinegar and cool the rice. Refer to the notes section below for details and to the video for visual cues.

Let rice cool to body temperature (or all the way to room temperature, if you prefer) before using for sushi.