Mix flour, sugar, and salt. If butter is soft, mix in with your hands to pea sized crumbs. If butter is cold, grate it in.
Line a 9x13 pan with parchment and press it in.
Filling:
Melt butter and use the same bowl you used for crust, pour in butter, add flour, sugar, maple syrup, milk, mix up. Then add eggs and vanilla. Whisk well.
Pour over crust. Sprinkle pecans all over the filling.
Bake for 20 minutes, then rotate pan and go another 15 minutes. Check if set, if not, bake another few minutes.
Cool completely before slicing.
Notes
Use walnuts for a cheaper option. You can also use raw sunflower seeds or pumpkin seeds to make nut-free bars.