How the R sound looks and how it is made:
The tongue is pressed high and back, as the tongue presses hard into the teeth. The jaw is slightly elevated, and the lips are open. The vocal cords vibrate during the production of this sound. The feeling with this is that the tongue is bunched up in the back of the throat, while pressing into the back molars. It’s like the pirate sound, argh!
Lipreading.org