Mix salt into the iced/cold water and stir until dissolved. Reserve 2 tbsp for later.
1 tbsp salt, 200 ml water
Place the flour in a large mixing bowl. Pour the salt water over the flour (except for the reserved amount). Using your finger tips in the shape of claws, mix the flour and salt water together until they bind into fluffy strips.
400 g plain flour / all purpose flour
Add remaining 2 tbsp of salt water and knead with the thumbs and palms of your hands, gradually forming a rough ball shape.
Place the dough ball in a thick plastic bag and spread out using your feet. When it becomes approximately 20 cm / 8 inches wide, hop off and fold the dough over itself four times (like closing the lid of a cardboard box). Pop it back in the plastic, and spread again with your feet. Repeat this around 20 - 30 times (not a typo - this is how you get that perfect udon texture!).
Remove from plastic and fold up into clam shape. Press edges into centre of the ball removing as much air as possible. Place into a plastic airtight bag and cover with a tea towel. Rest in a warm place for 30 minutes.
Remove from plastic bag onto floured surface and press dough into a flat circle with the palms of your hands. Dust liberally with cornstarch and roll out using a rolling pin until 1 cm / ½ inch thick.
cornstarch / cornflour