Place fish in an 8- x 8-inch baking dish; rub with 2 teaspoons salt, garlic, thyme, and fennel. Arrange peppercorns and chile peppers in dish. Pour 1/4 cup oil over fish mixture. Cover and chill 8 hours.
Add just enough remaining olive oil to cover fish (about 3 cups).
Bake at 200° 1 hour and 15 minutes or until fish flakes with a fork. Cool; remove fish from pan, reserving oil mixture.
Heat 2 tablespoons reserved oil mixture in a large nonstick skillet over medium-low heat. Add onion; cook 15 minutes or until golden, stirring often.
Drain chickpeas, reserving 1/3 cup liquid. Add chickpeas, spinach, reserved chickpea liquid, 1/4 teaspoon salt, and black pepper to onion mixture. Cook onion mixture 7 to 10 minutes or until thoroughly heated and spinach is wilted, stirring occasionally. Serve fish over spinach mixture. Top each serving evenly with red bell pepper strips, olives, lemon juice, and 1 teaspoon reserved oil mixture.
*If you can't find red arbol chile peppers, you can substitute cayenne or serrano peppers.