I am attempting to make a great Halloween cake. My goal is to make a spooky cake with gravestone and a zombie or skeleton coming out of the grave. I was able to practive making some great looking head stones and the base of the zombie/skeleton using RKT and fondant. However, I wanted to also make a hand coming out and a creepy tree and am having the hardest time with this. It seems no matter what I do I can't get the shapes to hold well.
Any suggestions?

Whenever I make fondant figurines I add tylose to it and it helps the fondant from sagging, makes it stiffer and dry faster.

Ditto divinecc. Or I use modelling chocolate.

I made a cake something like that last year for my dh to take to work. My grandson came up with the idea. I had a candy mold for the skull and hands.
You can see it in my photos. The haunted house was also a candy plaque.