Preheat oven to 350°F.
Line a baking sheet with parchment paper.
In a bowl, stir together flour, brown sugar, cinnamon, and salt.
Add melted butter and mix until crumbly.
Stir in chopped pecans.
Spread mixture evenly on the baking sheet.
Bake 15–20 minutes, stirring halfway through, until golden and crisp.
Let cool completely; it will harden as it cools.