Combine the lukewarm water, instant yeast, neutral oil, sugar or honey, and salt in a large mixing bowl. Add the bread flour and mix until no dry pockets remain.

The dough will look rough and feel sticky. Do not add additional flour. Cover the bowl and allow the dough to rest for 15 minutes. This rest gives the flour time to absorb the water and makes the dough easier to strengthen.

With damp or lightly oiled hands, lift one side of the dough, stretch it upward, and fold it toward the center. Rotate the bowl and repeat until all four sides have been folded.

Cover the bowl and rest the dough for another 15 minutes. Complete a second round of stretching and folding.

The dough should begin feeling smoother and more elastic after the second set of folds. Cover it and allow it to rise at room temperature for approximately 1 hour, or until noticeably expanded and airy.

While the dough rises, combine the chopped apples, sugar, lemon juice, cinnamon, flour, and 2 tablespoons of water in a medium saucepan.

Cook over medium heat for 4 to 5 minutes, stirring frequently, until the apples begin to soften and the liquid thickens slightly. Add the remaining tablespoon of water only if the mixture becomes too dry.

Remove the filling from the heat and allow it to cool. Hot filling can weaken the dough and interfere with the final proof.

Line a 9 × 13-inch baking pan with parchment paper. Coat the parchment and exposed sides of the pan with additional neutral oil.

The oil prevents sticking, encourages browning, and helps create the crisp edges that contrast with the tender center.

Transfer the risen dough to the prepared pan. With lightly oiled hands, gently stretch it into a rectangle.

Spread half of the cooled apple filling over the dough. Fold the top third of the dough toward the center, then fold the bottom third over it, similar to folding a letter.

Carefully turn the dough so the smooth side faces upward. Gently shape it to fit the pan without forcing out the trapped air.

Cover the pan loosely and allow the dough to proof at room temperature for approximately 1 hour.

The dough is ready when it looks puffy, has expanded toward the edges of the pan, and slowly springs back when gently pressed with an oiled fingertip. If it springs back immediately, give it more time.

Preheat the oven to 425°F using the conventional, nonconvection setting.

Spoon the remaining apple filling over the proofed dough. Coat your fingertips with oil and press firmly into the dough to create deep dimples. Press straight down without tearing or completely deflating the dough.

Bake for 23 to 28 minutes, until the focaccia is deeply golden around the edges and fully baked through the center.

If the top browns before the center is finished, loosely cover the pan with foil for the remaining baking time.

Allow the focaccia to cool in the pan for approximately 5 minutes before adding the glaze.

Whisk together the powdered sugar, vanilla extract, and milk until smooth.

The glaze should be thick enough to remain visible on the bread but fluid enough to drizzle. Add more milk ½ teaspoon at a time if it is too thick.

Drizzle the glaze over the warm focaccia. Allow the bread to cool and the glaze to set before cutting it into 20 pieces.