In a small bowl, combine the warm water and yeast. Set aside for 10 minutes, until foamy.

Into the bowl of a stand mixer with a paddle attachment, add the flour mashed potatoes, and 2 teaspoons salt. Mix on low for 1 minute to combine.

Coat a large bowl with 1 tablespoon of olive oil. Shape the dough into a smooth ball then lightly press it into the bowl, coating the bottom side with olive oil. Turn the dough over to coat the other side. Cover with a damp kitchen towel. Set aside for 1 hour to rise.

Grease a baking sheet with 1 tablespoon of olive oil. Press the dough down then spread it onto the prepared baking sheet. If your dough is springy and won't stretch to cover the pan, let it rest for a few minutes then continue stretching. Cover loosely with plastic wrap and let rise for an additional 1 hour.

Move a rack to the bottom third of the oven. Preheat the oven to 425°F.

Using your finger, gently press the dough all over making small indentations, or "dimples". Drizzle with the remaining 1 teaspoon of olive oil and sprinkle with the remaining 1/4 teaspoon salt. If you are including additional optional toppings, add them now.

Bake for 20 minutes, until golden brown. Let the focaccia cool for 10 minutes then slice and serve warm.