In a bowl, mix the 500g flour, 420ml water, yeast, and tomato paste (if you're using it). Stir it together and let it rest for 30 minutes.
Stir in the salt and olive oil. Cover it up and let the dough rise for an hour.
After an hour, gently fold the dough by bringing the corners to the center (yes, just like a letter!).
Repeat the folding process. This helps develop that airy texture!
Do the same thing one last time, folding the dough in again.
Oil the tray or line it with parchment paper. Transfer the dough onto the tray and let it rest for another 30 minutes.
Oil the focaccia surface and Gently press your fingers into the dough to create little dimples, and sprinkle with herbs salt.
Top with the boiled potato pieces, bacon or pancetta slices, and fresh rosemary.
Bake in a preheated oven at 250°C (480°F) for 20-25 minutes, starting on the lower oven rack to ensure a crispy bottom. Keep an eye on it to make sure it's golden and fluffy!
