In a mixing bowl, combine the ground beef, Italian-seasoned bread crumbs, sea salt, black pepper, and egg until just combined; avoid overmixing.
Portion the mixture into 12 equal pieces and shape each into a meatball about 1 to 1 1/4 inches in diameter.
Place the flour on a plate and lightly dredge each meatball, shaking off excess flour.
Heat a large skillet or Dutch oven over medium heat and add 3 tablespoons olive oil.
Add the meatballs in batches and brown on all sides, about 6 minutes total; they should be browned but not cooked through. Remove meatballs and set aside on a plate.
Wipe out excess grease from the skillet if desired, then pour in the pasta sauce and bring it to a gentle simmer.
Gently add the browned meatballs to the simmering sauce, cover, and cook for about 20 minutes or until meatballs are cooked through.
Meanwhile, bring a large pot of salted water to a boil and cook the spaghetti according to package directions until al dente; drain.
Serve the meatballs and sauce over the hot spaghetti and garnish with grated Parmesan cheese.