Here is my succulent vertical planter. It's only a week and a half planted. And, since hens and chicks are not knows for their great root system, I really don't know how long to leave it flat.

Nice Anna! I'd leave it flat for at least four weeks. Then try gently tugging on a plant. If it pulls out easily leave it flat a while longer.

Anna, that is going to be one eye catcher of a hanging planter.