There's 2 ways to stop Ray: 1.) he misses shots and stops himself, 2.) defenses keys to stop our screens for Ray, meaning a 2nd defender jumps out to block the passing lane allowing the screened defender time to catch back up to get into Ray's mug.
It's very difficult to stop Pierce, you can try to triple team him and force him to drive into traffic for turnovers, but a lot of the times he makes the right passes and decisions with the ball getting his mates easy baskets.
A Pierce-centric offense is very effective and it's basically how we've built team "offenses" throughout Pierce's early career.