Sprinkle the yeast over the surface of the water. Let sit for 10 minutes or until foamy.
Pour the yeast mixture into a large bowl or a stand mixer fitted with a dough hook. Add the salt, honey and a cup and a half of the flour. Mix with a spoon or on low speed until a dough starts to form.
Start adding the flour, a 1/4 cup at a time, until the dough is smooth in appearance and slightly tacky to the touch. You may need all 3 cups of flour to achieve this consistency or you could need more or even less.
Place the dough on a floured surface and knead by hand for 5 minutes or until it feels like satin. Form the dough into a ball and transfer to a greased bowl. Cover the bowl with a tea towel and let rise in a warm place for an hour and a half or until doubled in size.
While the dough is rising, place the potato slices in a large bowl. Fill the bowl with enough water to fully immerse the potato. Add the vinegar and give it a quick stir. Let the potatoes soak for 1 hour.
Once the hour has passed, lay the potato slices in an even layer on top of a large tea towel. Place another tea towel on top and press to dry the slices. Leave to dry completely.
Place 3 of the 5 sliced scallions in a medium-sized bowl. Add the sour cream, goat cheese, garlic and lemon zest to the bowl. Whisk to combine. Cover and refrigerate until ready to use.
When the dough has risen, punch it down. Grease a 9x13-inch pan with some of the olive oil and transfer the dough to the pan. Stretch the dough to fit. Cover the dough with a tea towel and let rise again for about 30 minutes or until it fills out the pan. This is a good time to preheat the oven to 400°F.
Using your fingers, create divets on the surface of the dough. Drizzle the dough with half of the olive oil. It will feel like a lot. Layer the potato slices over top and drizzle with the remaining oil. Sprinkle the surface of the potato slices with salt and add dollops of the sour cream mixture.
Transfer the focaccia to the oven and bake for 30 minutes, rotating the pan once. Finish the bread under the broiler for 5 minutes or until the cheese is brown and bubbly.
While the bread is baking, place the bacon in a large cast-iron skillet. Fry the bacon until quite dark and crispy. Transfer to a plate lined with paper towel and set aside.
Let the bread cool in the pan for 10 minutes before removing. Top the focaccia with the remaining scallions and crumbled bacon. Slice the bread into 6 or 8 evenly-sized pieces and serve immediately.