Make the "sushi" rice: Rinse the rice and set aside. In a small pot, bring the water to a boil. Add rice and adjust heat to low. Simmer about 25 minutes or until the water is absorbed and rice is tender but not mushy. (If the rice is done but water remains, drain it off.)
While the rice cooks, combine the vinegar, sugar, and salt in a small microwave-safe bowl. Microwave in 30-second intervals, whisking in between until the sugar and salt dissolve. Place the vinegar mixture in the refrigerator to cool.
Remove the cooked rice from the heat. Gently stir in the cooled vinegar mixture until fully incorporated. Chill the rice until you're ready to build your salmon avocado bowls.
Make the salmon: For this recipe, use leftover salmon or try this for more flavor. Preheat the oven to 350°F. Place two 4-ounce salmon fillets on foil atop a baking sheet. Rub the fillets with the toasted sesame oil and sprinkle with garlic powder, salt, and pepper. Seal the foil packet. Bake about 10 minutes, until the fish is cooked through.
Pull it together: Add half the rice to each of two small bowls. Top with flaked salmon, sliced avocado, sesame seeds and red pepper flakes. I also tore a few pieces of the roasted seaweed to sprinkle over the rice. Serve the bowl with soy sauce if desired.