Preheat oven to 450 degrees F. Drizzle the olive oil into a 9x13-inch baking dish and use your hand to evenly coat the entire surface. Set aside.
Combine the ground beef, ricotta, eggs, bread crumbs, parsley, oregano, salt, red pepper flakes, and fennel in a large mixing bowl and mix by hand until thoroughly incorporated.
Roll the mixture into round, golf ball-size meatballs (about 1 1/2 inches), making sure to pack the meat firmly. Place the balls in the prepared baking dish, being careful to line them up snugly and in even rows vertically and horizontally to form a grid. The meatballs should be touching one another.
Roast for 20 minutes, or until the meatballs are firm and cooked through. A meat thermometer inserted into the center of a meatball should read 165 degrees F.
While the meatballs are roasting, heat the tomato sauce in a small saucepan over medium-high heat, stirring often.
When the meatballs are firm and fully cooked, remove them from the oven and drain the excess grease from the pan. Pour the tomato sauce over them. Return the meatballs to the oven and continue roasting for another 15 minutes.
*CLASSIC TOMATO SAUCE:
Heat olive oil in a large pot over medium heat. Add the onions, bay leaf, oregano, garlic, and salt and cook,stirring often, until the onions are soft and ranslucent, about 10 minutes.
Add the tomato paste and continue cooking for 5 minutes. Add the tomatoes and stir constantly until the sauce begins to boil. Lower the heat ad simmer for 1 hour, stirring every 5 minutes or so to prevent the sauce on the bottom of the pot from burning. Taste and season with additional salt, if desired. Remove the bay leaf befoe serving.