Heat the olive oil in small saute pan over medium low heat. Add the cumin, coriander, and mustard seed and heat until the seeds begin to pop. Immediately remove the pan from the heat, add the preserved lemon and set aside.
Meanwhile, prepare the carrot and fennel. Using a vegetable peeler, peel the carrots into long tangles. Place into a bowl. Slice the fennel on a mandoline as thinly as possible. Add to the bowl.
Finish the dressing by whisking the sherry vinegar into the pan with the oil and seeds and seasoning with salt.
Toss the dressing with the carrots and fennel, staring with 3/4 of the dressing and adding the rest as necessary. How much you need will really depend on the size of your carrots and fennel. Taste for salt and adjust as necessary.
You can either toss in the cilantro leaves and fennel fronds and serve or plate individually and top each portion with the cilantro leaves and fennel fronds.