Place the rice flour with salt in a mixer (I used the Thermomix), and give it a quick swirl.
Set it up for kneading and pour the hot water in a slow steady stream till mixed.
Add the oil and set it to knead mode for 2 minutes till it becomes a dough, or, simply stir with a pair of chopsticks.
Leave to cool covered for at least 10 minutes for the dough to cool to the touch while you make the filings.
Add the tapioca flour and enough water such that the dough become springy. Chinese call it QQ.
Dough is done.