Make the sauce: In a small bowl, whisk together 3 1/2 tbsp soy sauce, 1 tbsp sesame oil, and 1 tbsp ginger. Set aside.

Transfer 4 cups of cooked rice to a large bowl. Drizzle with 3 tbsp rice vinegar and 1 tbsp sugar. Use a wooden paddle or your hand with plastic gloves to stir and combine the ingredients evenly. Set aside.

Cut 12 oz salmon fillet into strips ¼ - ½ inches thick.

Place your sushi mat on a working surface and put a seaweed sheet on the bamboo mat. Spread the rice across the nori sheet, leaving 1/2 inch of space along the top and bottom edges. Arrange the filling: sliced salmon, 7 oz avocado, and 4 oz cucumber about 1 inch from the bottom edge of the nori sheet. Roll up the rice mixture over the filling and use the bamboo mat to lift and compress while rolling. Remove the mat once rolled.

Transfer the roll to a big plate and repeat the process with the remaining ingredients to make 6 rolls. Cut each into 8 pieces. Sprinkle with 1/2 tbsp white sesame seeds and 1/2 tbsp black sesame seeds.

Serve with the soy sauce mixture.