Stir in couscous spinach to boiling stock and cover. Turn off heat and let sit for 5-10 minutes.
Once couscous is cooked, fluff with a fork and gently stir in fresh spinach and white beans.
Transfer the couscous to a storage container and cover and refrigerate for at least 30 minutes to cool.
Mix together lemon juice, olive oil, salt and red pepper flakes.
Once cooled, remove the couscous from the refrigerator and stir in the lemon dressing. Add the olives, peppers, and tomatoes and gently stir to distribute among the salad. Return to refrigerator until ready to serve or proceed with serving.
When ready to serve, fluff the couscous salad with a fork and sprinkle with feta cheese if desired and serve.
Couscous salad can be stored for up to 4 days in the refrigerator. It can not be frozen.
If the salad appears dry after refrigeration, drizzle with olive oil and fluff with a fork.
Fresh spinach is best, but if you don't have it on hand, you can use ½ cup defrosted and drained frozen spinach. Add to the boiling stock at the same time you add the couscous. If using frozen spinach, add before bringing the stock to a boil.