This can be used for a variety of building styles, but I'm keeping it as simple as it is.

All you need to do to get the results shown below is to place modular stairs (you know, the little, short stairs) wherever you want your land sloped. You will have to shape the terrain you want with the modular stairs. Make the slopes as big or small as you like them. Then Place floor tiles all around and through the modular stairs. Now, just delete the stairs and tahdah!! You can then delete any tiles you want, sloped or not while maintaining the floor tiles you want.

A helpful tip: Place one floor tile on the actual tile your stairs will descend from, then place your stairs. This just keeps your stairs from going ballistic while you're are trying to place them.
There may be other ways, but I sure don't know of any.

Thank you SO much. I am currently making a modern prefab home and this is JUST what I needed. :D

Yeah, I didn't know anything about it until I began rearranging the walls in my picture studio. It was purely an accident.

I am coming to find that I learn more by goofing off in build mode and making mistakes than I do reading forums. Not that they're not helpful, but it never helps to add to the references. I only hope that one day, there will be a site that is strictly devoted to The Sims 2 "how to do everything tutorials". Especially one that covers Material Definitions thoroughly, but that is a distant possibility.

Beautiful, Thank you so much for sharing.

I agree with you, it would be really good to have a site like that, totally devoted to just tutorials and "How to".