Grease a 8-inch or 9-inch square baking pan with coconut oil or spray. Line the bottom and sides with parchment paper. You want parchment to overhang on at least two sides. This will help you remove later. Preheat the oven to 350 degrees Fahrenheit.
For filling: In a large saucepan, place the apples, cranberries, coconut sugar, 1 1/2 tablespoons tapioca starch, cinnamon, nutmeg, and salt. Pour water over ingredients, stir, and bring to a boil. Once at a boil, reduce heat and simmer for 3 to 5 minutes until mixture thickens. Remove from heat and set aside to cool completely.
For batter: In a large bowl, whisk together sorghum flour, oat flour, tapioca starch, cinnamon, oats, and coconut sugar. Add coconut oil, maple syrup, and vanilla extract. Stir until mixture is evenly coated.
To assemble: Take half of the batter and press firmly into baking pan. Pour the cranberry apple filling over bottom layer and spread evenly. Add the remaining batter evenly over top and pat down lightly with your hands.
Bake for 25 to 30 minutes or until the top starts to turn golden brown. Remove from oven and cool on a wire rack until completely cool. Chill in the refrigerator for at least 2 hours or overnight. To slice, use overhanging parchment to remove from the pan and transfer to a cutting board. Slice into squares with a sharp knife. Reheat bars before serving if desired. Pairs well with vanilla ice cream or coconut whipped cream.