Preheat the oven to 300° F and line a rimmed baking sheet with parchment paper or a Silpat mat.
In a large bowl, mix everything together. Don't worry about smashing some of the popcorn—you want it to be well coated.
Spread mixture in an even layer on a rimmed baking sheet. Transfer to oven and bake, stirring every 10 to 15 minutes, until crispy, about 45 minutes.
Remove granola from oven and season with more salt to taste. Let cool completely before serving or storing. You may get big chunks of brittle-like popcorn candy. Embrace it! I do not know how long this stores for exactly, as we ate it all in 2 days, but I imagine it will stay good for at least a week, though your popcorn may soften slightly.