Begin by rinsing the sushi rice under cold running water. Continue rinsing until the water runs clear, ensuring all excess starch is washed away. Once rinsed, drain the rice thoroughly.
In a medium-sized pot, combine the rinsed sushi rice with 1 1/4 cups of water. Bring the mixture to a boil over medium heat. As soon as it reaches a boil, reduce the heat to low, cover the pot with a lid, and let it simmer gently for 15 minutes. After the time has elapsed, remove the pot from the heat but keep it covered. Allow the rice to steam in the residual heat for an additional 10 minutes.
While the rice is cooking, prepare the seasoning. In a small bowl, whisk together the rice vinegar, sugar, and salt. To help dissolve the sugar, microwave the mixture for about 20 seconds. Stir until dissolved completely.
Once the rice has finished cooking, fluff it gently with a fork, then fold in the vinegar mixture, ensuring it's evenly distributed. Allow the seasoned rice to cool to room temperature.
Place a bamboo sushi mat on a clean, flat surface. Lay one sheet of nori, shiny side facing down, on the mat.
To prevent sticking, wet your hands lightly with water. Take about 1/4 of the sushi rice (approximately 1/2 cup) and evenly spread it over the nori, leaving a 1-inch border at the top edge.
Arrange a colorful line of julienned cucumber, carrot, avocado, thinly sliced bell pepper, and radish in the center of the rice-covered nori. Feel free to be artistic with your arrangement!
Starting from the bottom edge of the mat, gently roll the nori away from you, applying light but even pressure to form a tight roll. Once rolled, dampen the top border of the nori with a little water to seal the roll.
Use a very sharp knife to slice the sushi roll into 6-8 equal pieces. Wipe the knife with a damp cloth between cuts to ensure clean slices and prevent the rice from sticking.
Transfer the sushi rolls to a serving plate. Finish by sprinkling sesame seeds on top of each roll for an appealing garnish.
Notes
Serve on a bamboo platter with soy sauce, pickled ginger, and wasabi for an elegant presentation.