Preheat the oven to 250 degrees F (120 degrees C). Add puffed corn to a large bowl. Line 2 baking sheets with parchment paper.
Combine butter, brown sugar, and corn syrup in a saucepan. Place over medium-high heat and bring to a boil, stirring often. Boil for 2 minutes and remove from heat. Immediately stir in baking soda, maple extract, and salt.
Pour butter mixture over puffed corn and stir with a rubber spatula until evenly coated. Pour mixture evenly onto prepared baking sheets and spread into an even layer.
Bake in the preheated oven for 45 to 55 minutes, stirring every 15 minutes. Let cool completely before serving or storing into airtight containers.
