Little contraption that looked like a steel guitar, but with all the strings the same length, very thin, and very close together. The rice flour was mixed with ... whatever they mixed it with, rolled into sheets, placed on top of the wires, and pressed through with a correspondingly sloted wooden block. Sort of like a ginormous egg slicer. Poof, noodles drop out the bottom.
This is probably not the only way, but it's the one I know.