Cook the couscous for 10-15 minutes, or according to instructions on packaging. Drain and rinse when done.
Prepare the dressing. Add the mustard, avocado, lemon juice, garlic, salt and water to a blender or food processor and blend until smooth.
Add the couscous to a bowl, together with drained and rinsed chickpeas, red onion, tomatoes, olives, and spinach. Stir together.
Serve with the avocado dressing, as well as almonds and vegan feta as garnishes.
Store this couscous salad separately from the dressing in an airtight container for up to 4 days. I would recommend making the avocado dressing on the same day as you plan on eating the salad, but you can also keep it in an airtight container for up to 2 days.