Second in a series of definitive rock vamps for your consideration…
A slow, alternating C (I) and F (IV) chords over a C pedal point in dotted rhythm, great for rock ballads (a la “Wild Horses” and “Bridge Over Troubled Water”)…
The feel should be laid back and unrushed with lots of subtle dynamics. Also, notice how the thumb of the left hand is “ghosted” (felt more than heard).