Other than pushing the gumpaste flowers and leaves into the smoothed buttercream frosting, is there another way to attach the flowers/leaves to the buttercream?

Depending on how heavy the flowers are, I've always used a touch of buttercream or royal icing to the backs of the flowers or other decor and put on the cake. If you're using a crusting buttercream it should work fine. If they are very heavy you might have to use toothpicks or some other type of support.

I agree. A dot of buttercream on the back seems to work very well.

Catherine

Will that work on the side of the cake?

It should as long as the flowers are not too heavy.

Will that work on the side of the cake?

I'm facing the same dilemma - I made gumpaste flowers that might be a bit heavy to expect a dab of buttercream to adhere it solidly to the side of a two tier cake. I was thinking of using candy melts, that always works as a good glue but I never tried it on buttercream before. Maybe the toothpick idea isn't too far off?