Heat oil in a large stockpot over medium heat
Season pork shoulder roast with salt and pepper on all sides area
While roast is browning, use gloves and clean the chiles.
It is absolutely crucial NOT to wash the chiles with water. Washing them removes too much of the chile flavor. Cut or pull the stem end off, turn pepper upside down and gently squeeze seeds out of the chile, peeling the skin off as you go. There will be a few stubborn seeds and a few pieces of skin, don’t worry, they add more yummy flavor
Chop chile, set aside
Remove roast from stockpot, place on a large rimmed dish, to catch juices
Add onions to the pot, saute for a few seconds, stirring until translucent
Add garlic, stir to combine, cook only a few seconds, do not burn
Add 1 cup water to deglaze the pan, add chicken base, bay leaf, oregano, garlic salt, red chile powder, chopped green chile, and Rotel
Return roast to stockpot, add enough water to almost cover the roast, bring to a boil stirring occasionally, reduce heat, cover and cook for 3 hours
Test flavor of broth, add more salt and pepper to taste, if roast is tender enough (meat falling off the bone) remove meat from pot, using 2 large forks, pull meat apart and chop into chunks (cook additional 30 mins to 1 hour if the roast is still tough)
Return chopped meat to stock pot, cover, and cook over medium low heat for 1 hour
Mix cornstarch with water until there are no lumps, add to post and stir until sauce is slightly thickened