You do not have time to turn that into a ham by Christmas, but, you have plenty of time to turn it into a nice pork roast. You could inject it to get more flavor deep into the roast. But, one of the best parts of a roasted pig is the hams, and they get little more than salt, pepper and some vinegar. Once the pork has cooked up, it can be chopped or pulled and seasoned once done.
Top turn it into a ham, you need to put it into a cure solution, not a brine, and it will need to sit for a couple of weeks at least. You will also need curing salts or something like Tenderquik.
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