Preheat your oven to 400°F and line several large rimmed baking sheets with parchment paper to accommodate the batch.
Portion the 11 lbs of salmon into 28 individual fillets, approximately 6.28 ounces each, and pat them thoroughly dry with paper towels.
In a large mixing bowl, whisk together the harissa paste, garlic powder, sea salt, black pepper, and half of the olive oil to create a flavorful rub.
Coat each salmon fillet evenly with the harissa mixture and arrange them on the prepared baking sheets with space between each piece.
Toss the cooked chickpeas with the remaining olive oil and a pinch of salt, then scatter them in a single layer around the salmon on the pans.
Roast for 12 to 15 minutes until the salmon is flaky and the chickpeas are toasted and golden brown.
While the salmon roasts, thinly slice the red onion and sauté it with the baby spinach in a large pot over medium heat until the greens are just wilted.
Divide the spinach and onion mixture into 28 meal prep containers, creating a base for the rest of the ingredients.
Place one roasted salmon fillet and a portion of crispy chickpeas into each container.
Finish each serving with a bright squeeze of fresh lemon juice over the salmon and chickpeas before sealing the containers for storage.