Preheat oven to 325°F. Line a large sheet pan with parchment paper or a silicone baking mat.
Add oats to a large bowl and set aside. In a separate medium bowl, add peanut butter, honey, melted coconut oil, vanilla, salt, and cinnamon if using. Microwave for 20 seconds then whisk until smooth. Microwave another 20 seconds if needed (until mixture is smooth and easy to pour).
Use a spatula to scrape all the wet ingredients into the oats. Mix until ingredients are combined and well incorporated.
Bake for 7 minutes, stir and spread again in an even layer (see note 1). Repeat twice more for a total of 21 minutes bake time.
Remove from the oven and toss in the coconut flakes. It might feel too soft, but it firms up as it cools. If you want the chocolate to melt into the granola, sprinkle it on top after about 5 minutes of cooling and let it set without stirring. Otherwise, let the granola cool completely for 3–4 hours, then stir in the chocolate once it's fully hardened.
Video
Notes
Note 1: After each stir, spread the granola into a flat, even layer with as little overlap as possible for even baking and the best texture.Storage: Store at room temperature in an airtight container for 3 to 4 weeks. Keep out of sunlight. Do not refrigerate. Or (recommended) freeze it: Store in a freezer-safe bag for 3 months (or up to 6 if sealed tightly). Enjoy straight from the freezer.