Put the flour in a bowl and pour half of the water over it, with the yeast and sugar dissolved in it.
Start kneading, then add the remaining water several times, and finally salt and oil.
Continue to work until you have a completely amalgamated dough, even if still sticky.
Pour the mixture on the floured work surface and let it rest for 1 hour at room temperature.
At this point proceed with the folds (if you don't know what I'm talking about, take a look here).
Make the first 3 folds, let rest for 15 minutes, then repeat the folds 3 more times (4 times total), always with 15 minutes of rest between one time and another.
At the end (after the 4th folds) the dough should be much more homogeneous and compact.
At this point, insert the dough in a lightly oiled container, cover with cling film and leave to mature in the refrigerator for about 12-24 hours or until it has tripled in volume.
When it has tripled, pick up the dough, turn it over on a floured work surface and leave it at room temperature for 1 hour.
After resting at room temperature, begin to gently stretch and roll the dough with your fingers, slowly creating a rectangle roughly the same size as the pan you will use for cooking.
Lift the dough with lightly floured hands and arms and move it on the pan, lightly greased with oil.
Let it rest again for 1 more hour, then brush with water and oil
Bake in a preheated convection oven at 180 ° C and cook for 25-30 minutes or until golden brown: the high hydration focaccia is ready.