Heat the olive oil in a skillet over medium heat. Add the lamb chunks and brown them on all sides, then transfer to the slow cooker.
Add the onion, garlic, and bell peppers to the slow cooker along with the diced tomatoes, beef broth, smoked paprika, saffron, and thyme.
Season with salt and black pepper, then stir to combine everything.
Cover and cook on low for 7 to 8 hours until the lamb is tender.
Stir in the green olives during the last 30 minutes of cooking so they warm through without losing texture.