Grease the crockpot with non-stick spray.
Layer sliced apples at the bottom of the crockpot.
In a small bowl, mix sugar, cinnamon, and nutmeg. Sprinkle over apples.
Evenly spread the cake mix over the apple mixture.
Drizzle melted butter evenly over the cake mix.
Cook on high for 2-3 hours or low for 4-5 hours, until the top is golden brown.
Serve warm with vanilla ice cream, if desired.