In a medium bowl, mash the avocados with lime juice and ⅛ teaspoon of garlic powder until mostly smooth but still slightly chunky. Season with salt and black pepper to taste. Set aside.

In a small saucepan over medium-low heat, combine the refried beans, drained Rotel tomatoes, ancho chili powder, cumin, and the remaining ⅛ teaspoon of garlic powder. Stir until fully mixed, season with salt and pepper, and cook gently until hot, stirring occasionally.

Lay the tostada shells on a flat surface. Spread each with a generous layer of avocado mixture, followed by a spoonful of the warm bean mixture. Top with shredded lettuce, chicken, shredded cheese, pico de gallo, and finally, a dollop of sour cream.

Serve immediately so the tostada shells stay crisp. Add hot sauce or jalapeños on the side for extra heat if desired.