Combine rice flour, tapioca starch, and a pinch of salt in a large bowl.
Gradually pour in the water and whisk continously until the mixture turns into a thin batter.
Prepare a wok or fry pan that is big enough to fit the steaming pan or plate snuggly. (I used ¼ sheet baking pan).
Fill the wok with water and bring it to a rolling boil.
Lightly grease the bottom of a baking pan or plate and add in about ⅓ cup batter. (Don't over grease the baking pan or the batter will separate from the pan).
Tilt or shake the pan a little so the batter covers the bottom of the pan. (Be sure to stir the batter before each steam.)
Transfer the pan to the wok and let it fit snuggly or float on the boiling water.
Cover the pan with a lid and steam for 2-3 minutes.
When ready, uncover and place the pan on a cold water bath.
Brush the top of the noodle sheet with oil.
Using a spatula, lift the edges to loosen up the noodles. [You may store the noodles at this point].
To make the sauce, whisk together the sauce ingredients in a bowl until the sugar has dissolved.
To serve, cut noodles into your desired width and place them in a bowl.
Pour the sauce over, top with cucumber slices, sesame seeds, chile oil, toasted sesame seeds, and cilantro. Mix everything up and serve at room temperature or cold.