Prepare the onion, celery, carrots, garlic, and potatoes by chopping and mincing.
Add all of the vegetables to the slow cooker along with the broth, salt, smoked paprika, oregano, and thyme.
Stir well and cook on high for 4 to 5 hours or 7 to 9 hours on low.
Once the cooking time is up and the split peas are softened, add in the parsley, lemon juice, and ham, if you're using it. The soup is now ready to serve.