Preheat & Prep. To start, preheat oven temperature to 350 degrees F. Lightly grease an 8x8 or 9x9 pan.
Make Pear Filling. In a large mixing bowl, combine chopped pears, brown sugar, cornstarch, vanilla, cinnamon, nutmeg, cardamom, cloves, and a pinch of salt. Gently stir to evenly coat the pears, then add pear mixture to the prepared baking dish.
Make Crumble Topping. In the same bowl (no need for extra dishes!), combine butter, gluten-free oats, brown sugar, gluten-free flour, vanilla, and salt. Use a fork, a pastry blender, or clean hands to combine the crumble mixture until the dry ingredients are moist and clusters start to form.
Assemble. Sprinkle crumble topping over the pear filling. I like to try for a variety of shapes and sizes for the crumble--some larger pieces, some smaller pieces--and to leave a small border around the edge without crumble topping to allow the filling space to bubble.
Bake The Crisp in the preheated oven for 45-55 minutes, or until the filling is bubbling on the sides (this means the cornstarch is working!), and the crispy topping is golden brown. (If your crisp happens to brown quicker than you expect, you can cover the pan loosely with aluminum foil)
LET IT COOL. REALLY. Remove the pear crisp from the oven and cool 20-30 minutes before serving, if possible. This will allow the filling to set a bit. (It's thinner and more liquid when it's hot, but it will thicken and set as it cools.)
Serve & Store. Enjoy this delicious pear crisp with a scoop of vanilla ice cream or whipped cream and a drizzle of caramel sauce, for best results! Store leftovers covered in the fridge 2-3 days. (I don't recommend trying to transfer leftovers to an airtight container, since the crumble usually gets mixed in with the filling this way, and no one wants soggy topping!)