1) Bring Fertilized eggs with you try for a bigger Dino egg to be safe, you might need about 2-4

2) Drop egg close to nest but make sure its far enough away so that the Gigantoraptor will come out and won't aggro you while you are in the nest

3) Run into nest and "hide" in the nest and wait for baby to come into the nest

4) Mirror the movements of the baby

5) Repeat until tamed

Another thing you can do is bring a friend to pick up the mom with a Rhynio and you can the baby with no issues, I just wouldn't kill the mom as it might affect the taming process.

Last tip: Once tamed pluck feathers as they can be used in breeding to get higher Stat of parents

More Gigantoraptor Taming & KO Tips