Preheat oven to 350 F. Line a 9x13 dish with parchment paper so that the paper hangs over the sides. This helps to easily remove them once baked. Set aside.
In a medium bowl, whisk together the dry ingredients - almond flour, coconut flour, coconut sugar, cinnamon, allspice, salt and baking soda.
In another bowl, mix together the wet ingredients - melted coconut oil, eggs, vanilla extract. Fold wet ingredients into dry ingredients until everything is well incorporated and there are no dry pockets left. The batter will be thick.
Fold in carrots, raisins and 1 cup chopped walnuts. Spread the batter evenly in the baking dish and bake in the preheated oven for about 25 minutes, or until a toothpick comes out clean. Remove from oven and let cool.
Cream Cheese Frosting (see Notes for Paleo version)
While the carrot cake bars are baking, make the frosting. Combine the cream cheese and butter in a medium mixing bowl and mix with a mixer for a minute. Add powdered sugar in batches until frosting is smooth and creamy.
Once cake is cooled, spread cream cheese frosting evenly over the cake. Sprinkle the remaining 1 cup chopped walnuts on top and refrigerate for about 1 hour or until frosting is firm.