01 - Line a large rimmed baking sheet with parchment paper or a silicone baking mat. Arrange the graham cracker pieces in a single even layer, edges touching, to cover the entire surface.
02 - In a medium saucepan over medium heat, melt the butter. Stir in the brown sugar, maple syrup, vanilla extract, and kosher salt. Bring to a gentle boil, stirring constantly, and simmer for 2 to 3 minutes until the mixture thickens and turns glossy.
03 - Pour the hot caramel evenly over the graham cracker layer, then spread gently with a spatula to coat all the pieces.
04 - Scatter the chopped toasted pecans evenly over the caramel layer. Bake in a preheated 350°F oven for 8 to 10 minutes, until the caramel is bubbling across the surface.
05 - Remove the baking sheet from the oven and immediately scatter the chocolate chips evenly over the hot surface. Let stand for 3 to 4 minutes so the residual heat melts the chocolate, then use an offset spatula to spread it into a smooth, even layer.
06 - Sprinkle flaky sea salt over the chocolate if desired. Allow the bark to cool completely at room temperature, or refrigerate for faster setting.
07 - Once fully set, break the bark into irregular pieces. Store in an airtight container at room temperature for up to 1 week.