For the squash and sauce: Preheat the oven to 400 degrees F and place a rack in the middle of the oven.
Rub 1/2 tablespoon of the olive oil on each cut-side of the squash and sprinkle with salt and pepper. Place the squash cut-side up on a baking sheet and roast until fork tender, 45 minutes to 1 hour.
To test for doneness, insert a knife into the squash; it's ready when the knife goes through with little resistance. Cool the squash for at least 10 minutes. Scrape the tines of a fork lengthwise along the flesh of the squash to pull out the long, thin strands.
While the squash cooks, make the sauce. Heat the remaining 1 tablespoon oil in a large nonstick saucepan set over medium heat. Add the onions and garlic and cook, stirring occasionally, until the onions are translucent, 3 to 4 minutes. Add the carrots and celery, and cook until the carrots are fork-tender, 3 to 5 minutes. Stir in the crushed tomatoes, diced tomatoes, tomato paste, oregano, red pepper and bay leaf. Cover the pot, reduce the heat to medium-low and simmer for at least 25 minutes (the longer the better), stirring occasionally. Season with salt and pepper.
For the meatballs: Combine the ground beef, flour, tamari, tomato paste, salt, pepper, cayenne, garlic and egg in a large bowl. Form about 40 bite-size (1-inch in diameter) meatballs. Place the meatballs in the sauce and simmer until firm to the touch and cooked through, about 15 minutes.
Plate the spaghetti squash on serving plates and top with the tomato sauce and meatballs to serve.
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