Make the Dough: In a medium-sized bowl, combine the glutinous rice flour, white sugar, and salt. Mix well. Gradually add hot water while stirring to form a dough.
Shape the Balls: Take a small piece of dough and roll it into a ball. If you’d like to add a sweet red bean filling, gently press the center of the dough ball to create a small indentation. Add about 10 g (0.35 oz) of filling, then carefully seal and roll it back into a smooth ball.
Cook the Rice Balls: Bring a pot of water to a boil. Once boiling, gently drop in the dough balls. When they float to the surface, add a small splash of cold water to lower the temperature slightly. After they float up again, remove them with a slotted spoon and transfer them to a bowl of cold water to cool briefly.
Coat the Gyeongdan: Roll the rice balls in a bowl of your chosen coating until evenly covered.
Serve: Let the rice balls cool completely, then serve as a snack or dessert.
