Mix all the dry ingredients in a large bowl. Add 3 dl (1.3 cups) of warm water and olive oil. Knead thoroughly for at least 10 minutes. If using a mixer, eight minutes will be enough.
Reload the dough back to the bowl and cover it with a cover or plastic foil. Let it rest in the refrigerator for 12 to 24 hours. Make sure you have sprinkled the bowl with flour before reloading the dough.
When the dough has rested, allow it to get used to room temperature for about 30 minutes. Sprinkle the counter with flour, reload the dough and knead again. Grease the baking pan with olive oil, transfer the dough to the pan and let it rest for another 45 minutes while it's covered with a kitchen towel. Preheat the oven to 220 °C/428 F.
When the dough has risen, use a cup of warm water to stick your fingers in it before making the wells on the top of the focaccia. Generously cover with olive oil and add pieces of sun-dried tomatoes, capers, dry rosemary and coarse salt.
Bake at 220 °C/428 F for 30 minutes. After first five minutes cover the focaccia with parchment paper to prevent sun dried tomatoes and capers form burning.
When baked, allow it to cool for at least 15 minutes. If you won't eat it at once, store it covered with a wrap when the focaccia has completely cooled down.