Combine warm water, instant yeast, flour, and salt in a large bowl. Stir together until a shaggy, wet dough forms. Cover and let rise for 30 minutes.

Dip your fingertips in water and grab one “edge” of the dough in the bowl. Lift it up and fold it over the rest of the dough. Rotate 90 degrees and repeat this 3 times, until you have done 4 stretch-and-folds.

Cover dough and let sit for 30 minutes, then do another set of 4 stretch-and-folds. Cover dough and let sit for another 30 minutes.

Add 1 tablespoon of olive oil to a 9x13-inch baking pan and spread to coat the pan.

Dump focaccia dough into the pan and push to the edges of the pan with oiled fingers. If dough resists or shrinks, let it rest 10 minutes and push to the edges again. Cover the pan with a kitchen towel or plastic wrap and let the dough rise in a warm place for 1 hour, until very jiggly and puffy.

Preheat the oven to 475 degrees F (245 degrees C). Drizzle remaining olive oil on top of the dough and push in with your fingertips to create small dimples.

Bake the focaccia for 20 to 24 minutes, until golden brown. Remove from oven and let cool completely.

Meanwhile, for glaze: whisk confectioner’s sugar and milk together until smooth. Set aside.

When focaccia is cooled, use a wooden spoon to poke large holes in a 3x4 pattern about halfway through the dough.

Add jam to a ziploc bag and snip the corner. Squeeze the jam into the 12 holes to fill. Drizzle the glaze over the top of the bread and spread evenly. Let sit for 10 minutes, then slice and serve.