This is basically what I want done, composting and then burial under a redwood sapling. https://en.wikipedia.org/wiki/Human_composting

My plan, if I live old enough to be facing debilitating age-related illness is to organize all my assets to be distributed beforehand, then hike out into the middle of a dense forest where I cant possibly be found, dig a shallow pit to lie in, and die there by whatever means tickles me at the time.

There are no large predators where I live, so Id just be slowly dissected by the ants and the beetles.

Bene Gesserit burials in "Chapterhouse" sound like it: dig a vertical hole, put the body in with (presumably) biodegradable wrapping, plant a tree on it.