Is it okay to fill with buttercream, freeze, then carve? Or is it imperative that you fill when it's fully thawed?
When should I let the settling occur?
I'd appreciate the advice.

Freeze, fill then carve. After carving crumbcoat and then while the buttercream is crusting up it will thaw out and settle. I try to allow two hours at least for this step. Then you can cover with fondant.

Hope this helps!

thanks!