For Revit LT, you can create an In-place wall and model a void using those tools and then cut the Toposolid with this void There are a few other options too - You can create a family that cuts the site. You can also use the split tool to create another potion of the site - change its type and lower that section for the building. Or you can use the Shaft opening tool to cut all the way through the site and then create another Toposolid for under the building. These ways will allow either simple or more complex geometry creation and offer some level of flexibility. Hope this helps a bit.
Harlan Brumm
Director of Product Management, Revit Core Capabilities and Collaboration Services