Rinse the beans, drain, and place in your slow cooker.
In a non stick pan on medium heat, brown the ground beef, breaking it up with your spatula as it cooks, until no or very little pink is visible (it gets cooked more). Drain the beef.
Add the beef, onion, bell pepper, garlic, cumin, chili powder, black pepper, and salt to the slow cooker.
Pour in the beef stock, stir, then cover and set the slow cooker to High setting for 4 hours or Low for 8 hours.
At either the 4 or 8 hour mark, check the beans, if they are tender, stir in the diced tomatoes and tomato paste. Taste and adjust cumin and chili powder to your preference. Turn the slow cooker to Low and cook for another 30 minutes. Remove the lid during the 30 minutes of cooking for a thicker chili if desired.
Chili will keep well for several hours on Keep Warm setting and will thicken more and the flavors will blend further.
Serve with crackers and or cornbread, enjoy.