- Preheat the oven to 400°F. Place tostada shells on a baking sheet and bake for 5-7 minutes until crispy. 
- In a medium bowl, combine the shredded chicken, chili powder, cumin, salt, and pepper. Mix well to ensure the chicken is evenly coated with spices. 
- Spread a layer of refried beans on each tostada shell. 
- Top the beans with the seasoned shredded chicken. 
- Add shredded lettuce and diced tomatoes on top of the chicken. 
- Sprinkle shredded cheddar cheese over the toppings. 
- Add a dollop of sour cream on each tostada and garnish with fresh cilantro and avocado slices. 
- Serve immediately and enjoy!