When a dog dies you should bury them as soon as possible and ideally within a few hours of the dog dying a hole should be dug and the dog should be buried.
If the dog is not buried the same day and it's warm out the dog will decompose faster and flies and other bugs will begin eating at the dogs body.
Once a dog dies and you are able to you should get a hole dug right away and then bury the dog so that they don't decompose above ground.
Some people will wait at least 3 hours before burying their dog to ensure they are dead and that's okay too if you want to wait that long.
In 3 hours rigor mortis will set in and the dogs body will become stiff.