A variation is to put the body in a car or building which is then set on fire.
One advantage of burning is that clothing and any evidence on the body can be destroyed if the burning is done properly.
Potential pitfalls:
(1) incomplete cremation, leaving artifacts or identifiable remains
(2) leaving evidence (type of accelerant, tire tracks, etc)
(3) needing to transport a body
(4) being seen at or leaving the site
(5) attention drawn by the smell of burning flesh
(6) attention drawn by a large amount of smoke or flame
(7) having enough material to ensure complete cremation
(8) too many people involved
Optimize:
(1) use a secluded area or a crematorium
(2) acquire sufficient combustible material in advance
(3) sift the ashes for any metal artifacts or bone fragments
Disposing of a body by burning needs to be distinguished from killing a person by setting the person on fire.