Put pork belly slab on a flat surface.
Using an ice pick, nails, or skewer, poke holes on the skin- lots of holes . Pat dry the belly.
Flip the meat and rub it with salt, pepper and five spice powder. Making sure that all nooks is covered with the rub.
Filp the belly again and pat dry.
Put the pork belly on a tin foil and cover all side with the foil, leaving the skin open.
Refrigerate the pork belly uncovered, overnight to make the slab dry.
When ready to cook, pre heat oven at 350 F.
Brush the pork bell with vinegar and cover the pork belly slab with rock salt. I used coarse Kosher salt in this post.
Bake in a pre heated 350 F oven for 1 hour.
After an hour, remove the pork belly from the oven. Remove the salt from the skin. Try to skim off the rock salt as much as you can, so that the meat is not too salty.
Change oven setting to broil. and move the rack to the lowest level. About 10 inch far from the top. This is very important, because if the belly is close to the top, it will burn, so make sure the pork belly is far from the top.
Broil pork belly for 25 minutes.