Grind peppercorns, allspice, and coriander seeds finely
Place meats in a Dutch oven and mix in spice mixture and salt
Pour stock over meat mixture. Add garlic, thyme, and bay leaves.
Gently heat to a simmer on the stovetop while preheating oven to 275° F
Cover tightly and place in oven for 2.5-3 hours, checking regularly to ensure that the pork doesn't dry out
When the pork is falling apart and the moisture is almost entirely gone, remove bay leaves, thyme, garlic, and duck legs.
Drain the pork, reserving the fat. Pull apart into fine shreds. Pull the duck meat apart into fine shreds and mix back into the pork.
Place in a container and smooth the surface to even. Pour fat over to cover and leave in the fridge for at least 1 day.