Wash the fennel bulb and celery stalks thoroughly. Trim the ends of the celery and remove any tough outer layers from the fennel.

Thinly slice the fennel using a sharp knife or mandoline.

Chop the celery into bite-sized pieces to match the size of the fennel slices.

In a large mixing bowl, combine sliced fennel and chopped celery.

Drizzle with olive oil and lemon juice, then season with salt and pepper. Toss gently to combine.

Serve immediately, garnished with finely chopped fennel fronds if desired.