The pad is attached by 6 clips in a hexagonal pattern, shown by the arrows.

Starting from the top, insert an opening pick in between where the cup leather meets the plastic casing, push it in firmly, then twist it until you disengage the top clip.

Try not to damage or peel off the leather while doing this. It helps if you pry towards the speaker housing, not the leather cup.

Work round the back side, poking the pick in and twisting to disengage further clips until you can gently pull the cup away.

When re-assembling, make sure that the stitching line on the ear pad is facing the bottom.