Spray the bottom and sides of a 5-quart or larger slow cooker with cooking spray.
Place the old fashioned oats, nuts and/or seeds, flaxseed, cinnamon, and salt in the slow cooker and stir to combine.
In a small bowl or large measuring cup, whisk the egg whites until frothy.
Add the maple syrup (or honey), coconut oil, and vanilla extract. Stir to combine.
Pour over the dry ingredients in the slow cooker and stir with a wooden spoon until the ingredients are evenly moistened.
Cover the slow cooker, leaving the lid slightly askew so that steam can escape.
Cook on high (leaving the lid askew) for 2 to 2 1/2 hours, until the nuts are toasted and the granola feels dry to the touch, stirring the granola every 30 minutes.
Turn off the slow cooker, then stir in the dried fruit.
For maximum crispiness, spread the granola out onto a baking sheet to cool completely.
The granola will continue to crisp as it cools. You can also let it cool in the slow cooker, but it will not be as crisp.
