Heat a large dutch oven (I used a 7 qt one, but a 5 qt size should work too) over medium-high heat on the stovetop. Add olive oil and heat until shimmery. Add ground beef and ground chicken and season with 1/2 tsp salt and 1/4 tsp pepper. Brown the meat, breaking it apart with a wooden spoon as it cooks. Once the meat is mostly cooked through but still has spots of pink, add onion and garlic and mix to combine. Continue cooking until the meat is cooked through and onion and garlic are fragrant.
Add crushed tomatoes, diced tomatoes, tomato paste, grated carrots, chopped bell pepper, Flavor God seasoning, red pepper flakes, and remaining salt and pepper. Stir to combine all ingredients, then lower heat to a simmer and cover the pot.
Simmer the sauce, stirring occasionally, for 45 minutes. Taste and add more salt as needed as the sauce cooks. In the last 15 minutes of cooking, add the fresh chopped basil. Once the 45 minutes are up, remove the sauce from heat and stir in the baby spinach. Set aside.
In a separate pot, bring about 4 quarts of water to a boil with 1 tbsp of kosher salt. Add pasta, stir, and set timer for 4 minutes (the water will come back up to a boil during this time, but you only need to leave it in the water for 4 minutes total). After 4 minutes, drain the pasta, reserving 1/2 cup of the pasta water, and immediately add the pasta and reserved pasta water into the meat sauce and stir.
Note: The final steps depend on whether you'll be freezing the dish or eating it now. Follow either the "Freezer Prep Instructions" or "Eat It Now Instructions" as applicable.