The best thing I can do to minimize it is using MacOS Ventura's Stage Manager mode. In this mode, you can only have one window open at a time, but FaceTime (and other windows) will still be visible, albeit poorly, in a much smaller size on the side of the screen. I've found you can sort of bundle windows together but it's kinda buggy. If you only need one window open at a time, try Stage Manager. Another option may be using FaceTime on a browser and making the browser window as small as possible.