Have two UO .mul client folders.
Use one for the server (change it in the Config folder).
Use the other for the client on which you connect to a server (ex, in razor).
Go ingame, call unfreeze on a building.
This will take the items in the Server Client files, and generate static items ingame.
Erase those items, wipe them if you don't need aything in the area.
Save the server.
Close the server.
Go to the Server Client folder, copy the correct statics.mul and possibly also staidx.mul map to the Client folder.
Run the server.
Login.
See that nothing is there anymore.
Keep in mind that your client folder has to be updated manually.
When you do any actions ingame related to freeze/unfreeze, it will only affect the files in the directory you provided in the Config file.
Keep in mind that any edit is a potential mistake, so keep backups before starting a change-spree!
I hope that helps.
If you have any concerns or questions, do not hesitate to send feedback.