Preheat the oven to 350°F (175°C). Line a large baking sheet with parchment paper and lightly spray it so the caramel will release easily once cooled.

Arrange the graham crackers in a single, tight layer over the parchment. Cover as much of the surface as you can, breaking crackers to fit any gaps so the caramel has a solid base.

In a medium saucepan over medium heat, melt the unsalted butter. When fully melted, stir in the brown sugar. Keep stirring until the mixture looks smooth and even, with no streaks of butter on top.

Once the mixture begins to bubble gently, stir in the vanilla, chopped pecans, and salt. Let it simmer for about 2 minutes, stirring often. The caramel should thicken slightly and coat the pecans.

Carefully pour the hot pecan caramel over the graham crackers. Use a spatula to spread it toward the edges so every cracker is covered in an even layer.

If you like, sprinkle a handful of crushed graham crackers over the top for extra texture.

Place the tray in the oven and bake for about 6 minutes. Look for steady bubbling across the surface and slightly darker pecans, without very dark edges.

Remove the tray from the oven and set it on a heatproof surface. Let the bark cool completely at room temperature so the caramel can firm up.

Once fully cool, sprinkle flaky sea salt over the top. Break the bark into pieces with your hands or a sharp knife and serve.