In a large mixing bowl, combine flour, salt, and sugar. Cut in the chilled butter until the mixture resembles coarse crumbs. Gradually add cold water, mixing until the dough forms a disc. Chill in the refrigerator for 30 minutes.

Prepare the filling by dicing apples and mixing with brown sugar, cinnamon, lemon juice, and cornstarch in a bowl. Set aside.

Preheat oven to 375°F (190°C). Roll out chilled dough to a rectangle (12x16 inches) on a floured surface. Transfer to a parchment-lined baking sheet.

Spoon apple filling down the center of the dough. Cut diagonal slits on either side and fold over in a crisscross pattern, sealing the ends.

Bake for 25 to 30 minutes until golden brown and flaky. Cool for 10 minutes.

Whisk together powdered sugar, milk, and vanilla for the glaze until smooth. Adjust consistency as needed.

Drizzle the glaze over the cooled Apple Kringle and allow to set before slicing.