Prep and Cook Pork Bones: Soak pork bones overnight in water to draw out myoglobin. Drain, rinse, and then pre-boil aggressively, skimming off scum. Clean bones, then pressure cook with 3.5L water and pork trotter in Instant Pot on high for 45 minutes. Natural release, then add 1L water, garlic, and boil to emulsify for about an hour.
Make Ra-yu (Chili Oil): Heat canola and sesame oil, then add green onions, garlic, ginger, and Sichuan peppercorns to infuse for 45 minutes. Mix Korean chili powder and Ichimi Togarashi with a small amount of water, then strain hot oil into this mix. Let steep, then strain if desired.
Assemble Ramen: Prepare noodles as per linked recipe. Heat soup, prepare Tare and Chashu as per linked recipes. Combine Tare, soup, and noodles in a bowl, top with Chashu, green onions, and Ra-yu to serve.