Slabs are inclined with the "Incline objects" command from the slab toolbar.
To slope your slab;
Click on the Incline objects icon from the slab toolbar .
Select the slab you want to bevel and click the right mouse button.
From the dialog that comes up, determine whether or not to select objects around the slab.
Draw your reference line to determine the direction of the slope.
Make your settings in the incline options dialog.