Preheat oven to 375 degrees. Lightly oil an 11 x 7-inch OR 8 x 8-inch baking dish with coconut oil. Arrange half of the apple rounds in the baking dish; top with half of the sliced sweet potatoes. Scatter half of the ginger on top. Season with salt to taste. Arrange the remaining apples and sweet potatoes on top. Scatter with remaining ginger and season with salt to taste.In a small bowl, whisk together the lemon juice, water, honey and 2 teaspoons of melted coconut oil. Pour the liquid over the sweet potatoes. Cover with foil and bake 45 minutes.Meanwhile, put the remaining unmelted coconut oil, coconut palm sugar (or date sugar), flour and pecans in a small bowl; use your fingertips to create moist crumbs.Remove the sweet potato casserole from the oven and sprinkle the pecan crumbs on top. Return casserole to the oven and bake, uncovered, for 15 more minutes. Remove the casserole from the oven and allow to cool for 15 minutes before serving. Serve warm.