Place a few squares of plastic wrap on a work surface. Place a slice of sashimi or a few slices of cucumber in the center of the plastic wrap. If using wasabi, dab a little wasabi on each piece of sashimi.

Wet your hands and place a ball of rice on top of the sashimi or cucumber.

Using the plastic wrap, tightly wrap the rice into a ball and set aside. Repeat with the remaining sashimi or cucumber.

To serve, unwrap sushi ball and place on a platter. Garnish with your remaining optional toppings.