Heat olive oil in a large paella pan over medium heat.
Sauté the onion and garlic until translucent.
Add the red bell pepper and cook for another 2 minutes.
Stir in the Bomba rice, coating it with the oil and vegetables.
Pour in the seafood stock and add saffron. Mix well.
Bring to a simmer and cook for 10 minutes without stirring.
Arrange the shrimp, mussels, and calamari on top of the rice.
Add the green beans and season with salt and pepper.
Cover the pan with aluminum foil and reduce heat to low.
Cook for another 15-20 minutes until the seafood is cooked and rice is tender.