بسم الله الرحمن الرحيم
The sunnah method of slaughtering is that the head of the animal is up and facing Qiblah direction. However, after stunning the animal you may easily raise its head up and slaughter. However, if three blood vessels of throat are cut then it is valid and halal, but it is against sunnah to slaughter the animal in hanging position upside down.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.