By default, sorted items are placed starting from the top-left corner, filling row by row left to right. You can change this per-player with two independent settings.
Start corner
/clicksorted sort start-corner <TOP_LEFT|TOP_RIGHT|BOTTOM_LEFT|BOTTOM_RIGHT>
Controls which corner of the inventory grid receives the first sorted item. All subsequent items fill outward from that corner according to the fill axis.
Fill axis
/clicksorted sort fill-axis <HORIZONTAL|VERTICAL>
Controls whether items fill row by row (HORIZONTAL, the default) or column by column (VERTICAL) from the chosen corner.