In a stand mixer fitted with a bread hook (or in a large bowl with a wooden spoon), add the flour, followed by the yeast, sugar and 1 cup of water. Mix on low speed until it forms into a shaggy dough.
Add the remaining water and salt. Mix on low speed until all the water is incorporated. Then increased the speed to medium and knead for 5 minutes until smooth and elastic. The dough will be sticking to the sides of the bowl. (Alternatively, knead by hand for 6-8 minutes. You may need to oil your hands to prevent sticking).
Turn the dough out of the bowl and add the 3 TBSP of oil to the bowl and turn to coat. Add the dough back into the bowl. Cover securely with a beeswax wrap (or kitchen towel) and leave to rise until doubled (about 1 hour).
Oil a baking sheet. Turn dough out on the pan and stretch with your fingers into a large rectangle. Fold in the rectangle in half. Turn it around, stretch it again and fold in half again. Then let rest on the pan for 10 min.
Slowly use your fingers to stretch the dough to fill the pan. It should be relatively easy to do. If not, leave it another 10 minutes to rest and then try again. The dough should now form a fairly even layer filling the entire pan.
Cover with a kitchen towel and leave in the fridge until 1.5-2 hours before you want to eat it.
Remove pan from fridge, uncover and let proof for 30 min. Meanwhile, preheat your oven to 450 degrees.
Use your fingers to make dimples in the top of the dough all over. Drizzle with more old and sprinkle with kosher salt.
Bake for 25 min until nice and brown.
Remove from oven and let cool completely. It will be hard, but you must resist!