In Part 2, there will be a lot more movement with your left hand as it makes its way over to knock the guitar body. Make sure you have the guitar in a stable position so it doesn't sway too much with your arm and hand movements.
Tablature Reference
L.str = use left hand to slap the strings
L. bod = use left hand to knock the guitar body
R.str = use right hand to slap the strings
R. bod = use right hand to knock the guitar body
T = pluck with thumb
T Slap = slap string with thumb
M = pluck with middle finger
A = pluck with ring finger