I know it needs displacement textures but is that’s
My guesses -
The sand: sculpted plane with displacement; I’m guessing the erosion trails from the stones were sculpted once they were placed.
The boulders: modeled/sculpted, maybe with displacement for fine detail; perhaps a high to low-poly bake for rendering
The rocks/stones: particle system
A couple links:
I would especially call attention to his use of the AO pass to lift up the sand around rocks/pebbles to make them look embedded rather than just sitting i the sand.