I'm trying to determine the logistics (if it is even possible) for an ancient culture to burn a body within a hole in the ground. As I understand it, ancient pyres/cremation left more of the body afterwards then modern cremation techniques provide. Given my fictional culture's issues with death (and the taboos around it) I'm already have them burning the deceased. It occurred to me that if it's possible for them to dig a whole, build a pyre within it, and burn the body there, they would then be able to cover it over without having to collect the ashes and remains for disposal.
I've been looking up ancient cremation techniques in a variety of cultures, the technicalities of funeral pyres (how long it takes to burn a body etc), and trying to find 'burning in the ground' (and varieties there of), but so far have found no information that tells me if this technique is even possible.
If anyone can point me in a direction, give me links, or has any helpful information, I'd appreciate it!