To assemble cake, place 1 cake layer, brownie side down, on serving plate. Spread half of filling to within 1/4 inch of edge; top with 3/4 cup of the strawberry slices. Repeat with second layer, remaining filling and 3/4 cup strawberry slices. Top with remaining cake layer, top side up. Frost sides and top of cake with frosting. Garnish with remaining 1 1/2 cups strawberry slices. Refrigerate 1 hour before serving. Store in refrigerator.