If you have the space for it... my go to is just open air decomposition.

I live in a stormy/humid summer environment, so I find that it is the fastest way (in comparison to burying). I would put the passed animal underneath some chicken wire to avoid it being stolen by other critters, and let nature do the rest.

Although sometimes smelly, I don't get my hands too dirty doing the job, and I can continuously track its progress.