Place large metal bowl in freezer.
Put 8 quart pot on medium heat . Add in stock, plus ½ cup water and bring to boil. Add couscous, cover and simmer for 8-10 minutes, or until liquid has been absorbed.
As couscous cooks, zest one lemon, juice all lemons for ½ cup juice yield. Whisk lemon juice/zest and mustard to combine. Drizzle in 1/3 cup olive oil to emulsify. Season with salt, pepper, and pinch of red pepper flake.
When couscous is cooked, stir in 1/2 of dressing, and place into metal bowl to rapidly cool. Place couscous into fridge to cool for a minimum of 30 minutes.
Right before serving, dice red pepper. Seed, peel and dice cucumber. Cube avocado. Mince handful of parsley. Stir couscous to gently break up**. Combine red pepper, olives, cucumber, avocado, arugula, parsley, and remaining dressing. Serve immediately.