Grease the slow cooker with butter or cooking spray.
In a large bowl, whisk together the flours, baking powder, baking soda, cinnamon, nutmeg, and salt.
In a separate bowl, whisk together the ground flaxseed, applesauce, dark brown sugar, melted butter, eggs, and vanilla extract.
Add the wet ingredients to the dry ingredients and mix with a wooden spoon until just combined.
Fold in the diced apples.
Pour the batter into the greased slow cooker and spread it out evenly.
Cover and cook on high for 2.5 hours or until a toothpick inserted into the center comes out clean.
Let the bread cool for 10 minutes before serving.