Line a half-sheet rimmed baking tray with parchment. Set aside.

In a large round bowl, combine flour, lukewarm water, olive oil, salt, and yeast. Use a bench scraper to bring the ingredients together until a soft dough forms.

Turn dough out onto a lightly floured countertop and knead by hand until soft and elastic, about 8-10 minutes.

Form dough into a ball and place in a well-oiled bowl, drizzling the top with even more oil.

Allow bowl to stand in a warm place, covered, for about 1 1/2 – 2 hours or until dough doubles in size.

Punch dough down.

Place on prepared tray and press into an 8-9-inch circle. Focaccia is supposed to be rustic, so don’t worry about being perfectly precise.

Cover the tray with plastic wrap, and place a towel on top. Allow dough to prove for one hour more.

Preheat oven to 400° F / 205° C.

Peel away the plastic wrap. Brush the dough with a generous amount of oil.

Add the grapes and capers, covering most of the surface. Use your fingers to push the toppings down and create deep dimples in the dough.

Drizzle about half of the remaining oil on top of the bread. Spritz lightly with water, then finish with the chili flakes and a sprinkling of sea salt.

Bake in preheated oven for 30 minutes, or until top and bottom are lightly golden brown.

Remove bread from the oven and pour remaining oil over the top.

Slice with a serrated knife. Serve warm or at room temperature.

Store leftover focaccia in an airtight container at room temperature for up to one day. Focaccia can also be wrapped in foil and frozen, then thawed at room temperature.