1heat oil in a 12 inch skillet over medium-high heat until shimmering. Add onions, garlic, tomato paste, oregano, anchovies, and red pepper flakes and cook until onions are softened and lightly browned, 8-10 minutes. Stir in wine, scraping up any browned bits, and simmer until thickened, about five minutes; transfer to slow cooker.
Stir crushed tomatoes, diced tomatoes, tomato sauce, and soy sauce into slow cooker. Cover and cook until sauce is deeply flavored, 9 to 11 on low or 5 -- 7 hours on high.
2Before serving, stir in basil and sugar and season with salt, pepper and additional sugar to taste.