Preheat oven to 375º. Line a baking sheet with parchment paper.
To make the meatballs, warm a large frying pan over medium heat, add oil, then the eggplant, onion, garlic powder, olives, sundried tomatoes, Worcestershire sauce, Italian seasoning and salt, and sauté 5 to 10 minutes, until starting to color.
Place oats and flaxseeds in a food processor and blend to form coarse crumbs. Transfer to a bowl and set aside. Place the sautéed mix, along with the basil, in the food processor. Combine roughly.
Transfer to the bowl with the crumb mixture, stir to combine, and leave in the fridge to thicken for 10 minutes.
Remove from the fridge and roll into golf ball-sized "meatballs" (makes around 12) and place on the prepared baking sheet; then bake in the oven for 20 minutes, or until golden brown.
Meanwhile, prepare the tomato sauce. Warm a saucepan over medium heat and add oil, garlic and sundried tomatoes. Sauté for a few minutes; then add diced tomatoes, basil and salt. Reduce heat to a gentle simmer and cook about 20 minutes, stirring every few minutes.
Serve the meatballs on a bed of spinach, if desired, and top with the tomato sauce and grated Parmesan, if you like.