Prepare the sushi rice: Rinse the sushi rice thoroughly in cold water until the water runs clear. Cook the rice according to the package instructions, preferably in a rice cooker. Once the rice is cooked, let it cool for about 10-15 minutes.
Season the rice: In a small bowl, mix the rice vinegar, sugar, and salt. Gently stir the mixture into the cooked rice, ensuring that it’s evenly distributed. Let the rice cool to room temperature.
Prepare the fillings: Slice your chosen fillings (e.g., fish, avocado, cucumber, etc.) into thin, bite-sized pieces. Set them aside, ready for assembly.
Assemble the sushi sandwich: Place a sheet of nori on a clean, flat surface. Spread a thin layer of sushi rice on top of the nori, leaving a small border at the edges. Add your desired fillings in the center of the rice. If you want extra flavor, you can drizzle a bit of soy sauce or spicy mayo over the fillings.
Fold the sandwich: Carefully fold the nori sheet to cover the rice and fillings, creating a sandwich-like shape. Press gently to ensure it holds together.
Slice and serve: Use a sharp knife to slice the sushi sandwich into squares or rectangles. Serve immediately with dipping sauces like soy sauce or teriyaki sauce.