Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, ensuring there is a little overhang on the sides to help you lift the bars out later.
In a medium bowl, combine the flour, softened butter, granulated sugar, and 1/4 teaspoon of salt. Use a pastry cutter or your fingers to mix until the mixture looks like coarse crumbs.
Press the crust mixture firmly and evenly into the bottom of the prepared baking pan. Bake for 15 to 18 minutes, or until the edges are just starting to turn a very light golden brown.
While the crust is baking, whisk the eggs, maple syrup, brown sugar, melted butter, vanilla extract, and salt in a large bowl until smooth. Stir in the chopped pecans until they are well coated.
Pour the pecan mixture over the hot, pre-baked crust. Spread it out evenly. Return the pan to the oven and bake for another 25 to 30 minutes. The filling should be set around the edges and only slightly jiggly in the middle.
Remove the pan from the oven and let it cool completely on a wire rack. For the cleanest cuts, refrigerate the bars for at least an hour before lifting them out by the parchment paper and slicing them into 16 squares.