Drying larger work carved green

[Nyman]

A few days ago I salvaged this largish chunk of firewood-to-be from a friend of mine. It's common aspen, eight inches in diameter, felled and halved around a year ago. Since then, it had lain stacked with the bark on, which means it was still rather fresh inside. In the attached picture, you can see the work in it's present stage.
Until now, I have simply kept it out of doors. Once I'm done, what should I do to minimise cracking and splitting while the wood dries? Should I hollow the sculpture at the back or leave it solid? How should I store it? What else should I pay attention to? I have only carved dry wood before this.

Markus