Scrape the skin of the Pacific saury lightly from tail to head to remove slime. Sprinkle with salt and let sit for 10 minutes. Rinse with water and pat dry with kitchen paper. Make shallow cuts on the skin and season with salt and pepper.

Slice the lemon and garlic thinly.

Line a baking tray with parchment paper and arrange the Pacific saury. Place garlic, lemon slices, and rosemary on top, then drizzle with olive oil.