If you understand the slab to slope rationally in one plane, make it with the roof tool.
If the slab will be facets of differing slope as might be with a sloping path, use a mesh.
In order to make a mesh of uniform sloping thickness, use the Goodie "Mesh to Roof" that converts the mesh into uniform thickness roof components.
Another way to trim the mesh is to copy the sloping mesh, elevate the copy downward equal to the slab thickness and use the SEO [Solid Element Operation] to subtract the mesh body.
Regular geometric ramps can be made with a variety of ramp objects.
Dwight Atkinson
