Spread the filling between layers to within 1/2 inch of the edges. When the layers are in place, press the top of the cake gently to make sure the cake is settled as much as possible. Allow it to stand for at least 1 hour to make sure the filling is set.
Next, spread a thin layer of frosting, called a crumb layer, to set the crumbs. After this coating is dry, spread frosting over the sides and top of cake to cover any imperfections from the first coat.