Bring a pot of water to a simmer. Start with high heat and then reduce to low once it boils. Add the short grain rice and salt. Cover. Simmer for 35-45 minutes until the rice is tender. If there is excess water, remove the lid and boil it off or pour through a wire mesh strainer. Toss with the rice wine vinegar.
Meanwhile, prepare the vegetables. Thinly slice the peeled carrots into long diagonal strips. Stack up and slice again into matchsticks. Repeat the same method with the daikon radish, or small radishes.
Thinly slice the green onion into long pieces.
If using sheets of nori, stack up several papers and slice into thin strips. Or serve the sheets at the table for people to pile in the rice & veggies.
Serve this sushi bowl with any other thinly sliced vegetables such as avocado or cucumbers when in season.
Serve the rice warm in individual bowls. Top with the vegetables or serve them on a platter at the table for guests to assemble their own. Sprinkle on strips of nori, additional rice wine vinegar, soy sauce and/or sesame seeds.