The techniques I used when creating the environment are taken from this youtube tutorial:
https://youtu.be/K7HruLyS-jE?si=5XF6PrdhnRp6znlq
The gist of his technique is using the Mesh Tools > Create Polygon Tool to draw out the basic shape of the platform of the island. From here, you retopologise, remesh, reduce, and triangulise (not in that order as you’ll see). Essentially, you work up in polys before reducing it back down to make the shape more organic.