If your iPad is plugged into a power source, you don’t have to press and hold the Home button to start Siri.
Simply say, “Hey Siri” and follow up with a request. This is perfect for when your iPad is charging on your desk or nearby and you can’t reach the Home button.
If you find that Siri is turning on accidentally then it can be disabled. Open Settings, select General, then Siri and turn off Voice Activation.