Direction of slab layout

Direction of slab depends on the place you click with your mouse on the selected region. Direction will be perpendicular to the edge of region, where you click with your mouse:

If you are using Create Panel layout for the Whole Floor, layout of slabs depends on selected supports, but sometimes it might do it in a different way, than you have expected. So to fix wrong areas, you can use Update Panel Layout for the Floor's Face and change orientation for one region: