Place sliced apples in the slow cooker.
Add 1/2 cup brown sugar, 2 teaspoons cinnamon, sugar and nutmeg.
Stir/toss to evenly coat apples.
Smooth apples into even layer.
In a large bowl, add oats, flour, 1/4 cup brown sugar and 1 teaspoon cinnamon.
Stir until evenly incorporated.
Using a pastry cutter of large fork, cut the butter into the mixture until it forms into crumbles.
Sprinkle mixture over top of apple layer in slow cooker.
Put a double layer of paper towels between top of slow cooker and lid to absorb excess moisture.
Cook on high for 2 1/2 hours or on low for 4 hours.
Remove lid and throw away paper towels.
You can serve with ice cream, if desired.