It's likely that the Force Touch sensor will stick to the display frame instead to the watch's body. In this case, insert an opening pick under the display and carefully separate the Force Touch gasket from the display.

To preserve the Force Touch gasket, pry carefully under the edge of the display. If the Force Touch gasket splits when lifting the display, or if you separate the gasket layers, you'll also need to replace the Force Touch gasket itself.

Slide the pick around the display to separate the adhesive between the Force Touch gasket and the display.

Don't insert the opening pick deeper than 1/16th of an inch (~2 mm) to avoid damaging other components.