A brief post to demonstrate the importance of using an armature when sculpting.
All this means is creating a wire structure, to which you then add sculpting material (in this case greenstuff) – lengths of wire were cut, then super-glued into place:
Very basic here; but it proves vital. On the one hand, it improves the adhesion of putty to flat surfaces; on the other, it provides a skeletal framework to guide you:
You can see where the armature was placed; and how layers of kneadatite were grafted on.