The body would not be flattened, any more than those of the fish which live down there. Soft tissues are made up mainly of water which is compressible only to a very limited degree, and bone would not be affected. Only those areas which contain air spaces that could not fill with water as the body descended would show much sign of pressure damage - notably the chest cavity. Bodies have been recovered from great depths and apart from the obvious rupturing of the lungs, ears, etc they are basically intact. We've all seen those drinking cups brought back from the depths and compressed by pressure, but that happens because they are made of a plastic foam material which contains mainly air.