Heat the oven to 400°F (205°C). Spread the refried beans in an approximately 11-cup rectangular glass dish. Mix the Greek yogurt, softened Greek cream cheese, hot sauce, and chili powder, then spread over the beans.
Mash the avocados with lemon juice, optional cilantro, garlic, and salt. Spread the guacamole evenly over the creamy layer.
Add the shredded cheese, salsa, green onions, and black olives.
Cut flour tortillas into trees and tombstones. Bake at 400°F for 5–10 minutes, until crisp and lightly browned. Cool, decorate, and insert just before serving. Serve with tortilla chips.