Rinse the rice thoroughly in cold water until the water runs clear, about 5-7 times.
Cook rice according to package directions, either in a rice cooker or on the stovetop.
While rice cooks, prepare sushi vinegar by combining rice vinegar, sugar, and salt in a small saucepan. Heat gently until sugar dissolves, then cool to room temperature.
Once rice is cooked, transfer to a large wooden or glass bowl (avoid metal bowls which can react with the vinegar).
Pour the vinegar mixture over the hot rice and fold gently with a cutting motion using a rice paddle or wooden spoon, being careful not to mash the grains.
Fan the rice while mixing to help it cool quickly and develop a glossy texture.
Cover rice with a damp towel and let it come to room temperature, about 10-15 minutes.
While rice cools, slice salmon against the grain into thin rectangles, approximately ¼ inch thick and sized to cover your rice balls.
Prepare a small bowl of water with a touch of rice vinegar for moistening hands (prevents sticking).
With moistened hands, take about 2 tablespoons of rice and gently compress into an oval shape with a flat bottom.
Place a small dab of wasabi on top of each rice ball.
Drape a slice of salmon over the rice, gently pressing it to adhere to the rice and wasabi.
Arrange on a serving platter and serve immediately with soy sauce and pickled ginger on the side.