A six-year-old boy who was subjected to "slapping healing" was not given insulin, was forced to fast for three days, and had his arms and legs slapped as he laid on a Sydney hotel bed dying and unable to breathe, a court has heard.

The child, who cannot be named, had Type 1 diabetes and was given his final insulin injection on April 22, 2015, at the beginning of a traditional Chinese medicine workshop at Hurstville in Sydney's south.

Hongchi Xiao has been charged with manslaughter after the death of a six-year-old boy. Credit:Facebook

His health deteriorated and he died five days later from diabetic ketoacidosis, a build-up of acid in the body after no insulin is administered.

The boy's mother, father, maternal grandmother and Chinese medicine practitioner Hongchi Xiao have been charged with manslaughter, with the Crown alleging each owed a duty of care to the boy that they breached through gross negligence. All have pleaded not guilty.