Hani-tai, as its square shape indicates, is heat energy circulating in a stable manner. It means that it is getting dry and firm. The process of change is over and has been completed, as the image suggests.
Hani and Verse 2593-2596
Hani is dry ground, clay. This is explained by its name, ha-ni. Notice how stable the ideograms ha and ni look.
The verse reads:
hani ukuru utuho ama-mitu naru kusa-ki utuho ha tasuku mitu hiyasu
Hani receiving rain from utuho makes grass and trees utuho helps water cools.
Ground receives rain water from utuho (light, in this case air). Grass and trees grow with the help of utuho and cooling water. Observe the second time, utuho is written with the ho allograph, implying heat of fire. This may refer to radiational/radiative cooling. These lines again allude to the cycle of water.
In any case, hani-tai is the solidification and completion of process, the building of land and mountains.