In a small bowl, dissolve the salt in the warm water. Sift the flour and starch into a second bowl.
Make a well in the flour bowl and pour about 1/2 of the water into the well. Mix with your hands scraping the bottom of the bowl as you mix until the water is incorporated – use a swift upward motion to "toss" the water into the dough, creating a sandlike mixture.
Add about 1/2 of the remaining water and continue to mix until the dough begins to separate into strands. Finally, add the rest of the water and mix and squeeze the dough together until it binds into a ball. The dough will not be smooth at this point. Let the dough rest in the bowl for 30 minutes.
Knead the udon dough until very smooth and shiny, either by hand or using a stand mixer. This will take a full 8 to 10 minutes using a stand mixer. Once the dough is smooth, form it into a tight ball and rub with a little olive oil. Place the dough ball into a clean bowl, cover with a cloth and allow to rest at room temperature for 3 to 4 hours.
Sprinkle your counter with flour and place the dough onto it. Roll to a 1/4–inch thickness.
Sprinkle the dough with starch, then fold the dough in half. Sprinkle with more starch and fold in half again. Let the dough rest 30 minutes.
With a sharp knife, cut the dough crosswise into noodles about 1/4–inch to 1/2-inch wide. Separate the noodles to prevent them sticking together