To make the filling:
Dice your spam in small bite-size cubes and transfer to a pan. Cook the spam, soy sauce, rice wine vinegar, and sugar on medium-high heat for 3-5 minutes, stirring frequently to prevent any burning. Cook until the spam becomes crispy.
To form + shape the rice balls:
Place a sheet of plastic wrap on a flat surface. Place ½ cup of cooked rice on the center of the plastic wrap and slightly flatten the rice into a disk shape with your fingers or a spoon.
Place 1-2 tablespoons of the spam filling in the center of the rice and carefully form the rice into a ball, making sure to cover the spam filling. Use the plastic wrap to easily form the rice ball into a triangle shape.
Remove the plastic wrap from the triangle rice ball and dip the sides of the rice ball in furikake seasoning.
