Preheat the oven to 350 degrees. Line a 9-inch square baking dish with parchment or foil and lightly spray with cooking spray.
Place the oats and nuts on a rimmed baking sheet and bake for 8-10 minutes until lightly toasted. Place the nuts and oats in a large bowl.
While the oats are toasting, add the honey, butter, and brown sugar to a small saucepan. Cook over medium heat until the butter melts and the sugar dissolves, stirring occasionally. When butter mixture is ready, remove it from the heat and stir in the vanilla and salt. Pour this mixture over the oat and nut mixture and stir to combine. Add any extra ingredients and stir to combine. Make sure none of the oats are dry.
Place all of the oat mixture in the prepared pan. Use a rubber spatula or the bottom of a greased measuring cup to press the mixture into the pan. Chill the granola bars for at least 2 hours. Lift the bars from the pan using the edges of the foil or parchment and place them on a cutting board. Cut into desired shape/sizes and serve.