Rinse the sushi rice under cold water until the water runs clear. Cook the rice with water in a rice cooker or pot according to package instructions.

While the rice cooks, prepare the sushi vinegar by mixing rice vinegar, sugar, and salt in a small bowl until dissolved.

Once the rice is cooked, transfer it to a large wooden or glass bowl. Gently fold in the sushi vinegar mixture while fanning the rice to cool it down.

Prepare all your fillings: slice the fish, avocado, and julienne the cucumber and carrot. Have everything ready for assembly.

Take a half sheet of nori and hold it in your hand. Spread about 1/4 cup of sushi rice over one half of the nori, leaving about 1 inch at the top edge.

Add your choice of fillings diagonally across the rice. Be careful not to overfill.

Roll the nori into a cone shape, starting from the bottom corner and rolling diagonally. Use a grain of rice to seal the edge if needed.

Serve immediately with wasabi, pickled ginger, and soy sauce on the side.