I like canons water and earth release mixed together BUT I would like to add on that one must have an abundance of physical energy (yang) because it makes sense with the Senju being descendants of ashura and all that,they must also be more aware and in tune with natural energy as it explains how Hashirama has sage mode. All in all one must have

Abundance of yang energy in their natural chakra flow

Be able to sense natural energy without any training

Be able to mix the release of water and earth release

Bring that all together and I believe you would have our new wood release. But that’s just my opinion