1. Fill a large bowl with cold water and Scrub the celery root thoroughly. Tip: an old toothbrush works well to scrub out any dirt caught among the roots.
2. Using a paring knife or a potato peeler, cut away the outer skin of the celery root in strips until the bare flesh is exposed all around.
3. Save the trimmings - frugal French chefs never throw them away because they add great flavor to stocks. Wash well, place in a freezer bag, squeeze out the air and freeze for up to 3 months.
4. Using a heavy chef's knife, separate the root from the greens making a flat surface.
5. Place the root flat side down on a cutting board and cut 5 to 6 thick slices.
6. Lay the slices flat and cut lengthwise into sticks, about as thick as the slices
7. Turn the sticks and cut into cubes. Place cubes in a bowl of water and lemon slice to prevent browning.