Score skin and fat. In a food processor, combine fennel fronds, fennel seeds, rosemary, sage, garlic, zest, salt and red pepper flakes. Add oil and pulse until it forms a paste.
Use the mixture to coat pork loin. Place in a large bowl and cover with plastic wrap. Refrigerate overnight or up to 2 days.
Remove pork from refrigerator at least 1 hour before you cook it. Preheat oven to 450F. Place pork on a rimmed baking sheet and roast for 25 minutes. Reduce temperature to 325F and cook for an additional 2-3 hours, until a thermometer inserted into the thickest part of the meat reads 180. Transfer pork to a cutting board and allow to rest 15-20 minutes before serving.
Meanwhile, bring a large pot of salted water to a boil. Cook the pasta according to package directions. Drain.
Bring another pot of salted water to a boil. Fill a large bowl with ice water. Add bok choy to water and cook until blanched, about 2 minutes. Using a slotted spoon, transfer to the ice bowl.
Divide noodles into bowls. Top each with fennel, green onions, bok choy, radishes and carrots. Add anchovy sauce to broth, ladle over noodles and top with pine nuts.