There are many different kinds of rice flour (Ssalgaru) but short grain rice flour (Maepssalgaru) is made with short grain rice and is used to make fluffy rice cakes like Mujigaeddeok (rainbow rice cake), among other things.
You can find this in the frozen section of a Korean grocery store. It’s sold frozen so that it’ll retain its moisture. If you can’t find it in a store, you can also make it at home with this recipe.
There is more information and discussion about making rice flour out of rice on the forum.