People talk more easily when seats face one another without forcing anyone to twist. A sofa and two chairs can create that invitation even in a modest room.
Shape the room
Angle the chairs slightly inward and keep a shared surface within reach. Avoid pushing every piece against the perimeter; a little air behind furniture can make the group feel intentional.
Let it earn its place
Conversation is a layout problem as much as a social one, and small angles can solve it.