To make the pie crust, add flour, salt, and sugar for the crust to a large bowl. Use a pastry cutter or two forks to cut in the butter until it resembles a coarse meal. The butter should be pea-sized or smaller. Drizzle over cold water, 1 Tablespoon at a time, bringing the mixture together with your hands. Stop adding water when the dough begins to form large clumps.

Use your hands to knead the dough until the flour is fully incorporated and the dough is no longer sticky. Form dough into a ball and wrap tightly with plastic wrap. Refrigerate for at least 2 hours.

When ready to bake, preheat oven to 375˚F.

Add all of the filling ingredients to a large bowl. Stir until combined and set aside.

On a floured, flat work surface, roll out chilled pie crust into an 18x13-inch rectangle. Place dough into a half sheet pan, and press up the rimmed edge. Trim the dough that hangs over the edges. Make sure to smooth out the crust so it fits into the corners of the pan.

Spread filling on top of the crust in an even layer.

Add oats, sugar, and flour for the crumb topping to a large clean bowl. Stir together until combined. Add butter and use a pastry cutter or your hands to cut in the butter until it forms a coarse crumb texture. Sprinkle evenly on top of the filling.

Bake for 40 to 45 minutes, until the crust is golden and crumble is toasty. Remove from oven and cool slightly in the pan.

While the pie is cooling, make the salted caramel. Add all the caramel ingredients to a medium saucepan over medium heat. Cook, whisking constantly, for 5 to 7 minutes, until thickened. Remove from heat and drizzle on top of the slab pie.