Prepare the Apples: In the mixing bowl, gently toss the sliced apples with the flour, granulated sugar, cinnamon, nutmeg (if using), and lemon juice.
Assemble the Filling: Transfer the apple mixture to the cast iron skillet, spreading it out evenly.
Make the Crisp Topping: In the same mixing bowl (no need to wash!), combine the rolled oats, flour, brown sugar, and cinnamon.
Add the Butter: Cut in the cold butter using your fingers or a fork until the mixture resembles coarse crumbs.
Top the Apples: Sprinkle the crisp topping evenly over the apple filling in the skillet.
Cook Over Campfire (or Camp Stove):
Campfire: Place the skillet over medium-low heat coals. You don't want direct flames licking the bottom, as this can burn the crisp. You can also use a tripod or grill grate to elevate the skillet slightly above the coals. Rotate the skillet occasionally for even cooking.
Camp Stove: Place the skillet over medium-low heat on your camp stove.
Cook: Cook for 30-40 minutes, or until the topping is golden brown and the apples are tender and bubbly. Keep a close eye on it to prevent burning, especially on the bottom. You can carefully lift the topping with a spoon to check the tenderness of the apples.
Cool Slightly: Let the apple crisp cool slightly before serving. It will be very hot!