Gather the ingredients.
On your cutting board, with a sharp knife, cut the pork roast into several large chunks. The chunks should be around the same size, but don't cut too small.
Jab a hole into a chunk and push a slice of garlic into the hole. Each chunk should have at least one piece of garlic in it. Larger chunks should have two.
Use one tablespoon of red Hawaiian sea salt. The Instant Pot intensifies salt, so you don't want to add too much. You can always adjust the salt level after the cook.
Sprinkle the salt on the pork chunks, covering all sides. Turn them over to make sure all sides are coated.Place the pork chunks in the inner liner of the Instant Pot, placing the larger chunks at the bottom.
Cut the onion into quarters, and put on top of the pork. Place the sprig of oregano on top, along with the Bay leaves.
Cut orange in half, and squeeze the juice over the meat. No additional liquid is needed, as the pork will add juices as it cooks.
Cook on high, manual pressure for 40 minutes. Let pressure release naturally after the time is up. I like to let the pin drop completely. (And often keep it on warm longer, this time it was on warm for 40 minutes.)
Remove the meat to a bowl or colander, reserving the juices in the pot.Remove the onion, bay leaves, and oregano sprig. I also like to remove the garlic pieces from the meat, but if you like lots of garlic in your carnitas, you can keep it in.
Take each chunk of pork, and slice it roughly, against the grain. Put the chopped meat into a second bowl.
Using a strainer, pour the pan juices from the pot into a measuring cup with a spout. If you have a lot of fat on your drippings, you can pour it off. I like to keep the fat, because I think it helps in keeping the meat juicy when reheating.
Pour about a 1/2 cup of juices into the bowl of chopped meat.
Put the rest of the pan juices into an airtight container to use in other recipes. You will also want to add some to the meat when reheating.