Step 1: Preheat your oven to 325 degrees F (160 degrees C).
Step 2: Line a baking sheet with parchment paper. This will prevent the crumble from sticking and make cleanup a breeze.
Step 3: Roughly crush the graham crackers. You can do this by placing them in a large zip-top bag and using a rolling pin or the bottom of a heavy pan to crush them into coarse crumbs. Alternatively, you can pulse them in a food processor for a few seconds.
Step 4: In a medium bowl, combine the crushed graham crackers, sugar, salt, and cinnamon (if using).
Step 5: Add the melted butter and vanilla extract (if using) to the bowl. Stir until the mixture is evenly coated with butter and the dry ingredients are well combined.