Place fennel seeds in a medium skillet over medium heat and cook, tossing, until fragrant, 2 to 3 minutes. Add chickpeas and 1 Tbsp. oil. Season with salt; sauté until warmed through, about 2 minutes. Transfer to a bowl to cool. In a separate large bowl, whisk remaining oil with lemon zest and lemon juice, oregano and mint. Season with salt and pepper.
Toss lettuce in a third bowl with 2 Tbsp. dressing. Arrange lettuce on a large platter. In the same bowl, toss chickpea mixture with 2 Tbsp. dressing. On top of lettuce, arrange each of remaining ingredients in rows. Serve with remaining dressing on the side.