Depressed Slabs

I'm sure this will end up in a dismal failure but here goes:

1. Manage --> Settings --> Object Styles --> Floor --> New --> Depressed Slab
2. Home --> Component --> Model in Place --> Floors --> OK --> Depressed Slab 1.75"
3. Void --> Extrusion --> Depth = 1.75" --> (sketch outline) --> Finish Extrusion --> Finish Model

Error "Some Void Forms of this family do not cut anything and will be deleted. To make a Void Form cut something else use the Cut Geometry tool."