Season the short ribs with 1 teaspoon salt and 1/2 teaspoon black pepper. Heat the olive oil in a skillet over medium-high heat and sear the ribs on all sides until browned, about 2 minutes per side. Transfer the ribs to the slow cooker.
Add the diced onion, carrots, and minced garlic to the slow cooker. Stir in the red wine, beef broth, and tomato paste until the tomato paste dissolves. Tuck the rosemary and thyme sprigs among the ribs.
Cover and cook on low for 8 hours or on high for 5 hours until the meat is very tender and pulls easily from the bone.
About 20 minutes before serving, bring the water to a boil in a saucepan. Whisk in the polenta and 1/2 teaspoon salt. Reduce heat to low and cook, stirring often, for 15 minutes until thick and creamy.
Remove the polenta from heat and stir in the butter and Parmesan cheese until melted and smooth. Discard the herb sprigs from the slow cooker. Serve the short ribs and sauce over the creamy polenta.