In a mixing bowl, combine the all-purpose flour and salt.
Gradually add the water to the flour mixture while stirring.
Knead the dough until smooth and elastic, about 10 minutes.
Wrap the dough in plastic wrap and let it rest for 30 minutes.
Roll out the dough to a thickness of about 1/4 inch on a floured surface.
Cut the dough into strips approximately 1/4 inch wide to form noodles.
Dust the noodles with cornstarch to prevent sticking.
Bring a large pot of water to a boil and add the udon noodles.
Cook for 8-10 minutes or until the noodles float to the surface.
Drain the noodles and rinse under cold water before serving.