Pat dry the pork with paper towels.
Combine salt, paprika, onion powder, and black pepper in a small bowl; whisk to combine. Take the rub and sprinkle it all over the pork.
Add 1 tablespoon olive oil in a large skillet and set it over medium heat; add the pork and sear for a couple of minutes on each side or until golden brown.
In a blender or food processor, combine the remaining olive oil, balsamic vinegar, and garlic; process until combined and thickened. Add Italian seasoning and whirl for just a couple of seconds to combine.
Add chicken broth to the insert of your slow cooker. Place the pork loin, fat side up, in the slow cooker. Using a pastry brush, brush the prepared balsamic mixture all over the pork loin.
Cover the slow cooker with a lid and cook on LOW for 4 to 5 hours or on HIGH for 3 hours.
Check for doneness by inserting an instant-read meat thermometer into the thickest part of the meat; pork is done when its internal temperature reaches 145˚F.
Remove the pork from the slow cooker and transfer it to a cutting board; cover the pork with foil and let rest for 10 to 15 minutes before slicing.