Most gingers need the tuber only to be planted just under the soil. The roots will grow down from them.

Look around practically any ginger plants and you'll see the rhizomes close to the surface. I'd only just cover them.

I just put mine down on the ground when I moved and forgot about it(not on purpose) I didn't realise how good it's doin I and don't even water it. great plant to have, I love the juice in the come as shampoo and hand lotion
Carmen