Soak the black-eyed peas in cold water overnight, then drain when ready to cook.
In a large saucepan, cook the salt pork over medium-high heat, stirring occasionally, until crisp and the fat is rendered, about 6 minutes. Add the onion and garlic and cook until just translucent, about 3 minutes. Stir in the chicken stock, drained black-eyed peas, ham, red-pepper flakes, 1 teaspoon salt and ¼ teaspoon black pepper. Bring to a boil, then reduce the heat, cover, and simmer over medium-low heat, skimming any foam that rises to the surface, until tender, about 1 hour.
Taste and season with more salt as desired. Stir in the rice. Cover and return the pot to a simmer over high heat. Reduce the heat to maintain a gentle simmer, cover and cook until the rice is tender, about 20 minutes longer. Remove from the heat and let stand, covered, 5 minutes, then serve.
