I know you said you don't want to use CAW, but if you change your mind, here are the instructions.
1. Build your lot in the game, as a residental lot.
2. Save it to the library
3. Make a empty world in CAW
4. Enter Edit in Game
5. Place a empty the same size as your lot
6. Place your lot in the open one
7. Exit Edit in Game
8. In CAW, change the lot type to community and the community lot subtype to what you want it to be
9. Open Edit in Game and save your lot to the library.
10. Share/ continue editing your lot, whatever else you want to with i