Preheat the oven to 350°F (175°C). Line a 9 × 13-inch baking pan with parchment paper, allowing excess to hang over the sides for easy removal.

In a large mixing bowl, combine the flour, granulated sugar, and salt. Add the cold vegan butter and cut it into the dry ingredients using a pastry cutter or two knives until the mixture resembles fine crumbs. Transfer the mixture to the prepared pan and press it evenly into the bottom to form the crust. Bake for 10 minutes, then remove from the oven and set aside while preparing the topping.

In the same mixing bowl, whisk together the brown sugar, brown rice syrup, non-dairy milk, melted vegan butter, cornstarch, and vanilla extract until smooth and well combined. Fold in the chopped pecans.

Carefully pour the pecan mixture over the partially baked crust. Use a spatula to spread the topping evenly across the surface.

Return the pan to the oven and bake for 25–30 minutes, or until the pecan topping is bubbling and appears set around the edges. Remove from the oven and allow the bars to cool at room temperature for approximately 30 minutes. Transfer to the refrigerator and chill for at least 2 hours to fully set.

Once chilled, lift the bars out of the pan using the parchment paper and slice into squares using a sharp knife. For cleaner cuts, trim the outer edges if desired.