Combine the ground beef, ricotta, eggs, bread crumbs, parsley, oregano, salt, red pepper flakes, and fennel in a large bowl and mix by hand.
Roll the mixture into round, golf ball-size meatballs, about 1 1/2 inch. Make sure to pack the meat firmly. Place in baking dish, carefully line them up snugly and in even rows vertically and horizontally to form a grid. The meatballs should be touching one another.
Bake at 350 for about 45 minutes, or until they are firm and cooked through. A meat thermometer inserted into the center should read 165.
When the meatballs are firm and fully cooked, remove them from the oven and drain the excess grease from the pan. Pour your sauce over them. Return the meatballs to the oven and continue roasting for another 15 minutes.