This is actually a difficult exercise to explain but a great lesson to learn. We demonstrate how to create a flat tapeing floor (or roof) where the underside of the floor (or roof) stays horizontal.
As well, the challenge is the floor edge has an elevation at the perimeter and an elevation at the interior where there is a donut hole (rectangular).
We use an in-place family using the ‘floor based’ template and set the catagory to ‘floors’ and then use a solid extrusion and a void blend. We also tie it all to grid lines for additional control.