Heat the water in a small pot over high heat until it boils. Add the olive oil and salt, stir in the couscous, and cover. Turn off the heat and let it sit for 10 minutes, until all of the liquid is absorbed. Use a fork to fluff the couscous. Don’t let the couscous sit for more than 20 minutes without fluffing it or it might clump up. You can fluff it and then recover it in the pot to keep it warm.