Peel and wash the celery, then cut it into 1 cm thick rounds. Slice the rounds into sticks, roughly the shape of French fries. Place the celery sticks on a baking tray lined with parchment paper. Drizzle with olive oil and sprinkle with salt. Toss well to coat. Bake in a preheated oven at 200°C (392°F) until crispy.