PreparationMake the Creamy Carrot-Radish Slaw: Whisk mayonnaise, oil, lemon zest, and lemon juice in a medium bowl until smooth. Add carrots, radishes, cilantro, parsley, almonds, salt, and pepper and stir to combine. Make the Chickpea Salad: Whisk mayonnaise, oil, salsa verde, lemon zest, and lemon juice in another medium bowl until smooth. Pulse shallot and garlic in a food processor until very finely chopped. Add chickpeas and pulse just until coarsely chopped, about 20 seconds. Transfer to bowl with salsa verde mixture. Fold in cucumber, feta, cilantro, and parsley; season with salt and pepper. Assemble the sandwiches: Layer 4 slices of avocado on each bottom bun. Top with a heaping 3/4 cup chickpea mixture and 2 Tbsp. spinach. Top with top bun and serve with carrot-radish slaw alongside. Do Ahead Chickpea salad can be made 2 days ahead. Chill in a resealable container. Cooks' NoteInstead of radish-top salsa verde, you can add an additional 1 Tbsp. chopped parsley and 1 Tbsp. chopped cilantro.