So I have seen several various designs of cremation urns carved on the carvewright over the years, but I now may be carving my first, for my wife's grandfather. I've read up on it some; seems like 200 cubic inches minimum, roughly one cubic inch per pound of bodyweight is the proper size. But I have a few questions...

Is there some liner, or some kind of inner container, which is used?
Or are the remains put directly into what is basically just a normal (if decorated) wooden box?
How do you seal it once the remains are in it - or do you?
Aside from the basic box design, are there any hints/tips you'd offer to me in making one?

Thanks!