Combine warm water and saffron together in a bowl.
Mix couscous and vegetable broth together in a saucepan; bring to a boil. Remove saucepan from heat, cover saucepan, and let sit for 5 minutes. Fluff couscous with a fork and transfer to a bowl.
Stir saffron mixture, celery, currants, olive oil, lemon juice, harissa, cumin, and sea salt into couscous. Refrigerate until chilled, at least 30 minutes.