You mix a bit of lye with water, heat it up and it will dissolve the body to a sludgy soup, leaving some traces of bone probably, but you can either dissolve those in acid, or crush them to dust and get rid of it that way. Apparently dissolving a whole body in acid can be quite hazardous though, and slower than lye.
Lye is also easy to access and cheap. So yeah. ^^
Lye is also easy to access and cheap. So yeah. ^^