Thinly slice the cauliflower on a mandoline or with a heavy sharp knife. Place in a large bowl and set aside.
Heat the oil in a small skillet over medium heat. Add the lemon slices, garlic, fennel seeds and coriander seeds and cook, stirring occasionally, until fragrant and the garlic begins to brown, about 4 minutes.
Remove from the heat and stir in the lemon juice. Pour the dressing over the cauliflower. Season with salt and pepper, sprinkle with parsley and chives and toss.