If your Dolphin is like my old one (1998), the wall next to the slide is tall panel mirrors. The clock, as someone said, is accessed by CAREFULLY removing the glass mirror panel. Use a flat blade paint scraper to get behind the mirror and pry gently. Velcro is industrial strength, so even, steady pressure is needed.
There is a National RV owners group on this site which can be of even greater help. Through FMCA there are several NRV Owners Clubs across the USA, Here in SoCal are The Dolphins,
The Dolphins. I suggest you join one, ore more of them and go camping with them Great bunch of folks, and LOTS of info on Nationals!
Good luck, and.......
Happy Trails!
Darryl