Peel, cut, and slice 8 cups of apples and place them in a medium-sized mixing bowl.
Sprinkle the sliced apples with 4 tbsp of sugar, 2 tbsp of flour or corn starch, 1 tsp of cinnamon, and 1/4 tsp nutmeg.
Stir the apples until they are evenly coated in the sugar mixture.
Spray an 8 x 8-inch baking dish with a little oil to prevent sticking, then pour the apples into the bottom of the dish and spread evenly.
Make the crumble topping:
Place 2/3 cup vegan butter, 1 1/2 cup flour, 1 1/2 cup oats, 1/2 cup brown sugar, 1/2 tsp cinnamon, 1/4 tsp nutmeg, 1/4 tsp salt, and 1/4 tsp baking soda in a mixing bowl.
Mix well until the butter is incorporated and you have a uniform crumbly mixture. (I find it easiest to use my hands for this step, but you can use the back of a fork or a pastry cutter.
Sprinkle the crumble mixture evenly on top of the apples.
Bake at 375° F for 35 minutes or until the top is crispy and slightly darker.
Let it cool for about 15 minutes before serving to let it firm up a little.