Bring a large pot of water to a gentle boil.
Add the rice flour, tapioca starch, and fine salt to the stand mixer bowl and mix briefly on low to combine.
With the mixer running on low, stream the 450g freshly boiled water down the side of the bowl and mix until the flour hydrates into a hot, thick, sticky paste.
Increase to medium speed and mix for 5 to 6 minutes, scraping the bowl once or twice, until the paste looks smoother and more elastic.
Cover the bowl and rest the paste for 10 minutes - it should relax slightly and become easier to pipe.
Check the texture while still warm: it should be thick, sticky, and pipeable, holding soft ridges that slowly slump back.
If the paste feels too stiff to pipe, mix in the held-back boiling water 10g at a time on low speed, using up to 50g first, then the additional 20g only if needed.
Load the warm paste into the disposable piping bag, twist the top tightly, and cut a hole 5mm to 6mm wide at the tip.
Pipe the paste directly into the gently boiling water, cutting the strands with scissors every 10cm to 12cm, working steadily without overcrowding the pot.
Cook for 3 to 5 minutes, or until the noodles float and look slightly translucent around the edges.
Lift the noodles out with a spider or slotted spoon and rinse briefly in warm water to remove excess surface starch.
Toss with a few drops of neutral oil only if the noodles need to sit for more than 5 minutes before serving.