First, the flowers will air dry and harden up enough so that you can handle them gently, but they stay soft inside. If you make these a week ahead of when you need to put them on a cake, people will still be able to eat them without breaking their teeth.
Second, you can use it without the flavoring as a practice buttercream. Pipe it out, scoop it up, and pipe it again. Since there's nothing perishable in it, it will be fine to use over and over. Just don't eat it if you're using it that way (gross).
Recipe for air dry buttercream:
1 pound powdered sugar
1 cup crisco shortening (no butter unless you'll be refrigerating them)
water to add to get to the consistency you want for piping. Start with about 1/4 cup and add as needed.
butter flavoring or vanilla flavoring or both
2 Tbsp meringue powder (optional)
Kara Buntin owns A Cake To Remember LLC, online cake supplies at www.acaketoremember.com and www.acaketoremember.etsy.com