Make sure everything is cleaned and possibly hairless. We won't have any problems with a bit of extra hair but not many like to see it on their plate. If pork knuckle hasn't come halved then cut them into halves along the long side. Place all the ingredients, except the salt into a big saucepan.
Fill the saucepan up with water and bring it to boil. Some like to discard the first boil of water. In this case the spices and herb shouldn't be added with the first batch of water but only with the second one.
When water reaches boiling temperature and the bubbles start to appear on the surface of the water, lower the heat.
Let it simmer for about 3 - 4 hours. When the meat easily comes off the bones it should be ready.
Salt to taste and let it cool off a little bit. Separate the liquid from the rest of the ingredients. A sieve will come handy at that but fishing out the bits is also an option for those who aren't in a hurry.
For a boneless aspic experience remove the bones from the meat. It should be fairly easy but very much greasy. Distribute the meat into the plates, bowls, cups or anything we've got at hand. A gallon of stock is pretty big batch considering that half of the volume is occupied by the meat.
Fill up the plates, bowls, cups with the soon to be aspic. Optimally the whole distribution process should be done where the jelly will set. Otherwise we have to move them one by one to a cool, dog, cat, pet or any animal free place. Cover the plates with another one, turned upside down if in doubt. A fridge will be perfect if it is enough place there.
Let it set for about 6 hours depending on the temperature. The cooler the room is the sooner it will set. Some fat may accumulates on top that can be scraped off if not desired and used up for later cookings. In the fridge, it can be kept for about a week but it can survive a couple of days at 68°F / 20°C. When it starts to liquefy again on its own with no apparent reason (e.g. heat), it shouldn't be consumed. Not like anyone could with a living taste bud.