Season the beef on all sides with salt. Add oil to a large sauté pan and heat over medium-high/high heat. Once the oil is shimmering, add the beef and sear until golden brown on all sides. About 3 minutes per side. Transfer the beef along with any fat to the bowl of a 6-quart slow cooker. Pour over ½ cup Korea sauce and toss to coat. Cook on low for 7-8 hours, until the meat is very tender and beginning to fall apart. Meanwhile, in a small bowl, whisk together the sour cream and 2 Tbsp Korea sauce. Refrigerate until ready to serve. Transfer the brisket to a cutting board (or leave in the slow cooker) and shred using two large forks or tongs, discarding any large pieces of fat. Return the shredded meat to the slow cooker and toss with juices and remaining 1 Tbsp Korea sauce. Season to taste with salt. Serve shredded brisket on warm flour tortillas with a drizzle of Korea-spiced sour cream. Top with Kimchi, cilantro and peanuts. Serve alongside fresh lime wedges.