In a large bowl, dissolve the yeast in the water. Mix well and add the two flours.
Either by hand or with a stand mixer fitted with the dough hook, mix until well combined. Add the salt and olive oil and continue to mix until well incorporated. If using a stand mixer, mix for two or three minutes until the dough is smooth. If mixing by hand, continue to mix with a wooden spoon and then with your hands by lifting up a corner of the dough and folding it back over the dough.
Rotate the bowl and continue in this manner. (it can get very messy with your hands but don’t be afraid - your hands are your best tools).
Let rise for two hours until doubled in size, performing a series of four folds every 30 minutes by lifting up one corner of the dough with a wet hand, pulling it up and bringing it back down on top of the dough on the opposite side. Turn the bowl a quarter of a turn and repeat 3 more times until all the dough has been folded upon itself.
Put in the refrigerator for a minimum of 12 hours.
Line a 17x11.5 inches (more or less) rimmed baking sheet with parchment paper.
Drizzle the parchment paper with olive oil and turn the dough out onto the baking sheet. If you want to use less oil, you can dust the parchment paper with flour and use lightly floured hands to stretch the dough out. Both methods are used in traditional schiacciata. Using slightly wet or oiled hands, pull and stretch the dough out into an even square/rectangle (or whatever shape you can manage; it can be a little challenging to spread out), pulling from the underside of the dough outward. Dimple it with your fingers (keep your fingers moist to keep them from sticking).
Let rise for at least 1 hour while the oven is preheating to 475° F (245° C). Check on the dough and if it has shrunk back, gently pull it out again within this one hour time frame, being careful not to deflate the dough too much.
Sprinkle with just a tad bit of water, drizzle with olive oil and salt well with a flaky salk like Maldon.
Bake for 13-17 minutes in the middle of the oven until golden brown and crunchy.
Transfer the schiacciata to a wire wrack and let cool completely before serving.