Hey,
my idea would be to use Dynamo.
1. Load the csv files into Dynamo
2. create a convex hull from all the points
3. create a convec hull from the lower points
4. substact the lower convex from the first one
5. create a directshape from the solid
I used two convex hulls cause it is quite complicatet to create the negative part under the slab without any more information than just the points from the csv.
soooo it might be more of a prototype script that works just for that given situation and not something that will work with every csv file.
