Assemble the hexes into the island — randomly, or in the fixed beginner layout.; Place number tokens on every hex except the desert; the robber starts on the desert.; In turn order each player places a settlement and an adjoining road, then in reverse order places a second settlement and road.
Why people argue about this
People often assume that the fixed beginner layout for the island is a permanent setup, forgetting that it's just one of two options: they can randomly place all hexes as per official rules or use this pre-designed map. This misunderstanding leads to arguments about which initial setup should be used without realizing there are multiple valid starting conditions.