Heat the olive oil in a large pot over medium heat. Add the pork cubes and brown them on all sides, about 6 minutes total. Remove the pork and set it aside.
Add the onion to the same pot and cook until it softens, about 4 minutes. Stir in the garlic and cook for 1 minute more. Sprinkle the flour over the onions and stir for 1 minute to form a roux.
Slowly pour in the chicken broth while stirring to avoid lumps. Return the pork to the pot along with the oregano, salt, and pepper. Bring the mixture to a simmer, then cover and cook on low heat for 45 minutes, stirring occasionally.
Add the artichoke hearts and olives. Continue simmering uncovered for 15 minutes so the gravy thickens further. Stir in the lemon juice right before serving.