Grind your spices. Annatto seeds are particularly hard. Unless you've got a lot of patience and a good molcajete, you're going to need a reserved coffee grinder for this. If you're an avid cook, it's a good idea to have several coffee grinders. One for savory spices, one for sweet spices, and of course, one for coffee.

Now, combine your spices and the remaining ingredients (minus the pork) in a blender, and buzz it till everything is blended smooth.

Cut your pork into chunks, 3-4 inches wide is fine. Doesn't need to be perfect by any means.

Place the pork in a large plastic bag. Pour the puree over it. Seal it up and set it aside. 3-4 hours should be enough, but I left it overnight.

About 5 hours before your target meal, pour the pork into a baking dish and cover with tin foil. Bake at 325F for about 4-5 hours. Check it at 4 to see how close you are. It should be super tender. If you pinch a chunk of pork with a pair of tongs and it falls apart easily, then you better get to rounding up the crew because it's time to eat. If it's still firm, hold tight. All the magic happens at the very end, so jumping the gun does nobody any good.

For a little more authenticity, line your baking dish with a banana leaf before adding the pork. Then, fold it over to tuck the meat in for the cooking. I'd still recommend the foil as a secondary coating though. The banana leaf lends a hint of flavor in my opinion, but they can be tough to find in some areas.