Step 1: Cradle the Nori
Place a half sheet of nori shiny-side down into your non-dominant hand, with one end right on your palm, and the other end extending up, cradled by your fingers.
Step 2: Rice it Up
Moisten your other hand in a 3:1 mixture of water and vinegar and pick up a handful of sumeshi. You should use about a 1/2 cup per roll. Place the rice directly on the nori above your palm. Spread it so that it covers about 1/3 of the nori, then make an indentation in the center using a wet finger.
Step 3: Stuffed
Add your stuffing to the roll, placing it in the indentation in the rice. Although hand rolls can take a bit more abuse than other types of sushi, do try not to overstuff it, or you'll have a hard time rolling it up later.
Try to use ingredients that give a contrast of colors and texture. In this case, I'm using blanched spinach, pickled carrots, and fresh leeks with a sprinkling of sesame seeds.
Step 4: Lift the Corner
Grab the bottom corner with your free hand and lift it up and across the rice, cupping the rice in your palm as you fold to create the beginning of a cone shape.
Step 5: Rolling Rolling Rolling
Continue to roll the rice into a tight elongated cone until just the far edge remains.
Step 6: Sticky Rice
Place a couple of grains of cooked rice on the last corner of the nori, then finish rolling. Use the rice grains to stick the nori in place so that the cone doesn't unfurl.
Step 7: Serve
Serve temaki as soon as they are done so that the nori remains crispy. When eating a handroll, dip only the corner of the nori in soy sauce as you eat—try to avoid saucing the rice, which can cause it to fall apart.