Using a fireplace requires work. You can’t just throw a body in and expect it to burn—or a limb, for that matter. Fireplaces are not incinerators. To do it properly, the body must be cut into small pieces, and the fire must continue burning so it can reduce as much as possible to ash. If it’s done right, only bone fragments and teeth will remain.
Slow and methodical…meanwhile it's bound to smell like roasting meat
