Heat oil in a small saucepan over medium-high heat; when it simmers, add ginger, cinnamon, cloves, coriander, cumin, star anise, Sichuan peppercorns, and chili flakes. Remove from heat and let sit until cool, at least 1 hour and preferably 2 or 3. Strain oil into a bowl or jar and discard spices. Put a pot of salted water over high heat and bring to a boil. Add celery and blanch for about a minute; drain in colander and run under cold water to stop the cooking process. Layer celery and tofu on serving plates, drizzle with chili oil and sprinkle with salt.