Evolve the mountain peak.
The size of the mountain peak is also related to the strength of the cultivator who evolves it.
In fact, Chu Ning, at the Foundation Establishment Stage, let alone evolving a mountain peak, would normally find it difficult to successfully cultivate the Immovable Mountains Technique.
Those Mountain Sect ancestors, Chu Ning conservatively estimated, would have to be at the Nascent Soul Realm or above before making a grand vow to cultivate the Immovable Mountains Technique.
That he could successfully cultivate the Immovable Mountains Technique at the Foundation Establishment Realm was due to the energy provided by the Longevity Fruit.
To evolve the mountain peak, one begins nourishing it based on the size of the peak, and the Nourish Mountain Technique recorded is precisely this method of nourishing the mountain peak.
Nourishing the mountain peak is simple: allow the peak to continuously absorb Earth Vein Spiritual Energy in order to grow.