Assuming you're using a sprint phone.. install the sprint2flip cab then install any flipclock you like..
First go to start/settings/today then to the "items" tab and uncheck tf3d.. install sprint2flip, restart your phone, go back to start/settings/today and recheck tf3d. You will have a flip clock.
Here is the sprint2flipclock cab:
http://forum.ppcgeeks.com/attachment.php?attachmentid=19322&d=1230078720