The Urantia Book makes no mention of cremation, except incidentally.
The various means of disposing of the body after death is never discussed as a moral issue for believers. The development of burial practices is explored, and of course, we know that in Jesus' day, burial in a crypt was customary.
Some churches frown on cremation, but—speaking just for myself—it seems that cremation is a logical and eco-friendly way to dispose of bodies, in a world in which space seems to be more and more at a premium—not to mention the eventual leeching into our soil and water of harmful chemicals used for embalming. This last point is only now begining to be discussed, and "green burials" are a new way of looking at burial.
This issue of the method of disposal of the human temple is one for the individual to decide. Since the essence of the human being has vacated the body, I would think that any respectful way of committing it back to the earth from which it came is acceptable.
The Urantia Book is far more concerned with the human soul, the eternal element of the human being, and not with rules and regulations for particular care of the physical body after death.
I hope you'll take the time to have a look at our flash movies—in particular, After You Die and You Can Live Forever which are brief, beautiful video presentations of Urantia Book teachings regarding death and eternal life. And please feel free to subscribe to Quote of the Day (a free service)—a daily inspirational quote.
Thanks for this question. Again, The Urantia Book is not a "rule book." It does give us a wealth of information from which we can formulate a philosophy of living based on our own depth of truth-seeking, and the lengths to which we are willing to go to amend our lives accordingly. But the revelation is not a religion, in and of itself.