I'm going to put a bouquet of silk Easter lilies on top of a 6" cake. I'd like to avoid inserting them directly into the cake because I want it to be able to be removed intact for cutting. How do I do that, O Cake Masters?

If they are silk, what I did was cut the stem off really close to the head of the flower, then using a blop of BC icing as glue, just laid them in place on top of the cake. No penetration necessary.

Sometimes I cut out a disk of fondant a little smaller that the top of the cake and the same color as the cake-or a contrasting color. (I ice my cakes in buttercream.) I attach any bows, figues, etc. to that disk and set it on top of the cake. I can easily life it off when it's time to cut the cake. Maybe that would work with your flower topper.
Here are some examples:

http://cakecentral.com/gallery/1902801
http://cakecentral.com/gallery/1593784
http://www.flickr.com/photos/hjscakes/

I thought I'd heard of people doing something like that. I'm icing it in buttercream but using purple ribbon to signify Christ's royalty. I could do a purple fondant circle. . . Thanks!

If they are real, you better check as I think lilies are poisonous.

Silk flowers...I think I would do as Debi suggested.

Oops! I read it again and see that you said they are silk.