Slow-Cooker Pork Shoulder Sugo

In large bowl, mix onions, carrots, celery, garlic, salt, oregano and red pepper flakes. Set aside. In 12-inch skillet, heat oil over medium-high heat. Cook pork shoulder 4 minutes on fattiest side, then turn and cook 3 minutes each on other 3 sides. Transfer to 6-quart slow cooker. Add onion mixture to skillet with pork juices; cook 5 to 8 minutes, stirring frequently, until beginning to brown. Add red wine; cook 1 to 2 minutes, stirring frequently, until all liquid is absorbed. Stir in tomatoes; cook 3 to 5 minutes, stirring constantly, until mixture thickens. Pour mixture over pork in slow cooker. Add stock and anchovies; stir liquid. Cook on Low heat setting 8 hours or High heat setting 4 hours. Transfer pork to cutting board; cool slightly. Cool liquid 10 minutes, then carefully puree in blender in batches, and return to slow cooker. Set slow cooker to Warm heat setting. Shred pork, discarding any pieces of fat. Add pork to liquid in slow cooker, and stir to combine.