Place chicken breasts in a baking dish. Pour BBQ sauce over the chicken, ensuring it's evenly coated. Bake for 20-25 minutes, or until the chicken is cooked through and tender.
Once cooked, remove chicken from the oven and shred it using two forks. Mix the shredded chicken with the remaining BBQ sauce in the baking dish.
Assemble the tostadas: Spread a layer of shredded chicken on each tostada shell. Top with shredded cheddar cheese, red onion, and fresh cilantro.
Add sliced avocado to each tostada and dollop with sour cream.
Serve immediately and enjoy!
Notes
For an extra kick, add a dash of hot sauce to the BBQ chicken mixture.