Heat the olive oil in a large saucepan over medium heat, and cook the onion until lightly brown.
Season with 1 teaspoon salt and pepper to taste. Pour in slow cooker and set to low while preparing meatballs.
In a bowl, mix the ground beef, almond flour or oats, oregano, garlic, parsley, eggs, and cheese. Season with salt and pepper. Roll into 1-inch balls (I use a large scoop from Pampered Chef) and drop into the sauce.
Cook meatballs on low until done, about 6 to 7 hours. (My slow cooker always cooks faster than recipes suggest; it took 5 hours.)
About 20 minutes before dinner, put zucchini through spiralizer. Cut long strands into shorter 10-in pieces, roughly. Saute (in batches if necessary) in 1 T. Olive oil and a little salt for about 4 to 5 minutes. Drain in colander, patting with paper towels (it can be watery.) Serve the meatballs and sauce over the zoodles (or serve over spaghetti or as meatball subs on rolls, if you prefer).