Make sure the cake layers have level, even tops. Use a sharp serrated knife to level them off or a cake leveler.
Place one layer of cake on a cake turntable if using or on the cake stand. Fill with an even layer of buttercream then top with the second cake layer. You can turn the cake layer upside down so that the bottom becomes the top to make sure the cake is more level. Repeat this step until the 3rd, top layer of cake.
Using an offset spatual or bench scraper, lightly cover the top of the cake with a thin coat of buttercream.
You can now cover the sides with a light coat of buttercream, smoothing it out with the bench scraper or spatula. Alternatively you can just leave the sides naked and have the buttercream peak out between the layers.
Clean and dry each flower from petal to stem. Wrap the stems in plastic wrap if you are inserting them into the cake. Lightly cover the top of the cake with clear plastic wrap so the cake is safe from the flowers.
Arrange the flowers around the cake