Watch the Permanent Pivot online guitar lesson by Brad Carlton from Chord Studies: Slash Chords Vol. 1
This progression is a I-V/I-vi-V progression in the key of G. Like in our first example the slash chord will be the V/I. Starting off with the G5, to get to the D/G you simply lift your little finger and barre the first three strings with finger one. Your third finger will act as a pivot throughout all four chords.