Patience makes perfect. Take the time to chill or freeze your baked layers before assembling the cake. The layers will be less fragile, and you'll have more control and better results with frosting. While they're chilling, line your serving plate with 2" to 3" wide strips of parchment paper.
Pipe a rope of frosting around the outside edge of the cake layer. Refrigerate for 15 minutes so it will become firm. This "dam" keeps frosting or filling from bulging out the side of the finished cake. After the dam sets, fill the top of the layer.
Trim the next layer and place it cut side down over the first. Chill the cake again, if it isn't cool to the touch.
Smear a very thin coat of frosting on the sides and top of the cake.
Once the crumb coat is firm, cover the top and sides of the cake with a finish coat of frosting. Gently remove the parchment paper strips.
Decorate and embellish to your heart's content.
For more cake success, see our post on how (and why) to crumb coat a cake.