Pre-heat oven to 350 degrees F. If desired, prepare baking sheet with silicone mat or parchment paper.
On a large, ungreased cookie sheet (jelly roll size, which is about 18x13) arrange the graham crackers, breaking if necessary. Set aside.
Melt butter with brown sugar in a medium saucepan over medium heat. Heat until it comes to a boil then allow to boil for 2 minutes, stirring constantly.
Remove from heat and add the vanilla and salt.
Pour mixture over graham crackers, spreading it evenly to the edges.
Sprinkle the crushed pecans evenly over the graham crackers.
Bake for 12 minutes in preheated oven.
Remove from oven and allow to cool slightly.
Cut into squares and cool completely on wire racks.
Notes
Use high quality butter for best results. Some lower quality butters will have a higher water content and might cause the sauce to separate.If your sauce breaks, or separates, stir it well to try to bring it back together. Or try using an immersion blender to help emulsify it.