Cut your pork into roughly 1.5" chunks and season with the salt. Then, in a large pot preheated to medium high with about a teaspoon of oil, sear on two sides in 2 or 3 equal batches for about 3 minutes per side, until they have a good brown crust on them.
Throw all the seared carnitas back into the pot and add onion, garlic, bay leaves (and optional cumin and oregano) into the pot and mix, letting the onions saute until they start to turn translucent. (A minute or two.)
Squeeze all the juice from the orange and lime into the pot then add the water and vinegar.
Bring to a boil, covered, for a minute or so. Once it's been boiling for a minute, turn the heat down to medium low and simmer, completely covered, for 45 to 60 minutes, stirring occasionally. (Maybe every 15 minutes or so.)
Check the seasoning at this point - you might like more salt or a little more acid from the citrus.
Then simmer for another 15 minutes with the lid askew.
Your carnitas should be moist, delicious, and fork tender by this point. Enjoy!
