How do cooks prepare belly pork in a restaurant? In a similar style to the question on preparing risotto in restaurants..

When cooking belly pork, to a texture that's soft, tender and still moist, long cook times at a low temperature (around 150 degrees celsius for 3 to 4 hours) are generally required, yet when ordering it in a restaurant it obviously doesn't take that long to arrive at the table!

My question therefore is, what tricks or techniques do restaurant chefs use to serve belly pork on demand. Can it be cooled and re-heated later, or is there another "trick" that's used?
No trick. It's par-cooked, cooled, and held cold until service. Then when it's on order, you finish the cooking. That is true for most long-cooked dishes.