Gear mentioned in this thread:
Kansui (sodium carbonate) (baked baking soda)
No set proportions as there as so many variables
Start with approx:
2tsp sodium carbonate
100g water (soft)
225g AP flour
Kneed to bring together - let sit for 1 hour in fridge
Kneed again until it's nice an pliable - use a large pin as the dough is very hard. Pro's use a pole that they sit on utilizing body weight.
Let rest overnight in fridge.
Roll or stretch as desired.