Heat the oven to 350°F. Lightly coat an 8x8-inch baking pan (about 2 inches high) with cooking spray. Line the bottom and sides with 2 sheets of parchment paper positioned perpendicular to each other so that the parchment hangs about 2 inches over all 4 sides of the pan to form a sling.

Beat 1 stick room temperature unsalted butter, 1/4 cup granulated sugar, and 1/2 teaspoon kosher salt with the paddle attachment in a stand mixer on medium speed until creamy, about 2 minutes. Scrape down the sides of the bowl with a flexible spatula.

Beat in 1 cup all-purpose flour on the lowest speed just until a crumbly dough forms, about 30 seconds. Transfer to the baking pan and use your hands or the bottom of a flat measuring cup dusted with flour to press it into an even layer.

Bake until the crust is golden-brown around the edges, 20 to 22 minutes. A few minutes before the crust is ready, make the pecan filling.

Whisk 3/4 cup corn syrup, 1/4 cup packed brown sugar, 2 large eggs, 2 tablespoons all-purpose flour, 1 teaspoon vanilla extract, and 1/2 teaspoon kosher salt together in a large bowl. Stir in 1 1/2 cups pecan pieces.

Pour the filling onto the hot crust and spread into an even layer.

Bake until the filling is set and dark golden-brown, 25 to 30 minutes. Place the pan on a wire rack and let cool completely, about 1 1/2 hours. Refrigerate for at least 1 hour or up to overnight. To serve, grasp the excess parchment and lift the slab out of the pan and onto a cutting board. Cut into 12 bars.