Heat oil in a skillet over medium heat. Cook garlic slices in hot oil until lightly toasted, about 30 seconds.
Pour 1/2 cup chicken stock over the garlic; add cranberry beans, corn, tomato, currants, lemon zest, salt, and black pepper, respectively, and stir. Sprinkle 1 pinch oregano over the beans mixture.
Bring the mixture to a simmer, reduce heat to medium-low, add another splash chicken stock, and cook at a simmer, stirring occasionally and adding more broth to keep mixture from becoming dry, until the beans are completely tender, about 45 minutes.
Stir remaining oregano into the beans mixture; transfer to a plate and garnish with lemon zest.