First, make sure the slab style has no tapered components.   With the Slab Drainage Tool: Add a drain at the two corners to be the lower side of the slab. Connect the two drains. Move the control points for the valleys (that are closest to the high side of the slab) to the corners to be the highest side. Edit the two valleys and use the "Define by Elevation" option with an elevation of 1". Voilla! 🙂   ScreenFlow.mp4