Wash and peel your celeriac and cut it into slices as thin as possible. I used a mandoline slicer for this. Gently massage salt into the celeriac slices without breaking them. Let it sit for 20-30 minutes so the structure of the celeriac breaks down a little. Bring sugar, vinegar, water, and salt and pepper to a boil. Scald a large pickling jar and place your celeriac slices inside. Pour the liquid over the slices, close the lid, and let it sit for at least 4 hours but preferably refrigerated overnight. The next day you will have delicious pickled celeriac that can be used to add acidity, sweetness, and crunch to many dishes.