Place couscous in a fine strainer and rinse under cold running water. Dump couscous onto a sheet pan, sprinkle with salt, and let stand until grains swell, about 10 minutes. Break up lumps with your fingers.
Partially fill a large steamer pot or stockpot with 1-inch water. Bring water to simmer. Place damp tea towel in steamer or colander and add couscous. Fold towel over couscous. Steam, covered, over simmering water for 15 minutes.
Pour couscous onto large, rimmed baking sheet and sprinkle with 1/2 cup cold water. Toss with slotted spatula until cool and the water is absorbed. Spritz hands with olive oil and spread out couscous, breaking up any lumps as you go. Set aside for 5 minutes.
Refill pot with enough water to make 1-inch again. Return couscous to colander or steamer and steam, covered, for 10 minutes.