Heat the olive oil in a large skillet over medium-high heat. Add the lamb shoulder chunks and brown them on all sides for about 6 minutes total. Transfer the lamb to the slow cooker.
In the same skillet, add the chorizo slices and cook for 3 minutes until they release some fat. Stir in the onion, garlic, and red bell peppers. Cook for 4 minutes until the onion softens.
Sprinkle the smoked paprika over the skillet mixture and stir for 30 seconds. Add the diced tomatoes, beef stock, salt, and black pepper. Bring to a quick simmer, then pour everything into the slow cooker over the lamb.
Cover and cook on low for 7 to 8 hours until the lamb is fork-tender. Stir once halfway through if possible.
Taste and adjust salt if needed. Serve hot with the chopped parsley scattered on top.