Prep the pork: Pat the pork dry and season all over with salt and pepper.
This helps the meat sear well and seasons it from the inside out.
Sear for flavor: Heat olive oil in a large skillet over medium-high. Sear the pork in batches until browned on at least two sides, about 2–3 minutes per batch. Transfer to the slow cooker.
Build the base: In the same skillet, add onion, carrots, and celery with a pinch of salt.
Sauté 3–4 minutes until slightly softened. Stir in garlic and tomato paste; cook 1 minute until fragrant. Scrape everything into the slow cooker.
Add remaining ingredients: Add bell pepper, diced tomatoes with juices, broth, beans, potatoes, Worcestershire sauce, smoked paprika, cumin, thyme, and bay leaf.
Stir gently to combine.
Cook low and slow: Cover and cook on Low for 7–8 hours or on High for 3.5–4.5 hours, until the pork is fork-tender and the vegetables are soft.
Finish with greens: In the last 10 minutes, stir in the spinach or kale. Taste and adjust seasoning with salt and pepper.
Serve: Ladle into bowls and top with chopped parsley. Squeeze a little lemon over each bowl if you like a bright finish.
Serve with crusty bread or over cooked grains.