Preheat the oven to 350 degrees Fahrenheit.
Peel and core the apples and slice into thin strips. I usually peel them, then slice into four sections going around the core, then thinly slice each of the sections to about 1/8-1/4 inch thick. You can also use a mandoline to slice if you prefer.
Add the apples to a very large bowl with all the remaining filling ingredients. Toss to combine.
In a second bowl, combine all the crumble topping ingredients and mix together with a spoon until well combined. It shouldn't be wet or dry, just crumbly.
Toss about 1/3 of the crumble mixture with the apples.
Add the apples to a 9 inch cast iron pan or 8 or 9 inch regular baking dish and spread evenly. It might seem like it's overflowing a bit, but the apples do shrink a bit as they bake.
Use your fingers to evenly sprinkle the rest of the crumble mixture on top.
Add to the oven, uncovered, and bake for 45-55 minutes or until the top is golden brown and the apples are bubbling underneath. It can sometimes get messy, so I usually put a cookie sheet under the pan/baking dish to catch any drips. You don't always need it, but better safe than sorry! The bake time will vary slightly depending on your pan. You'll know it's done when the top is golden and the apples are bubbling. If the top starts to brown too much before the inside is done, cover with foil until it finishes baking.
Remove from the oven and let cool for 10 minutes. Serve warm with vanilla ice cream or whipped cream and homemade vegan caramel sauce.