If you want to cook the chili on the stovetop, use a pot large enough to fit all the ingredients. If you'll be cooking in the slow cooker, you can simply use a large skillet to cook the ground beef.
Cook the ground beef until cooked through and drain the fat.
To a blender, add the celery, onion, carrots, green onion, spinach, garlic, and beef broth. Puree until liquid.
In the skillet you cooked your beef in, pour the green sauce over the meat and cook on medium, stirring frequently, until the beef has absorbed the green sauce. This is how you have so many hidden vegetables in your chili! It looks a little weird to have “green meat” in the skillet, but once it is in the chili, it's not green anymore! Cook until the meat has absorbed most of the green sauce.