Prepare the Chicken: In a small bowl, mix together seasoning salt, garlic powder, and pepper. Rub this mixture all over the chicken breasts to season them thoroughly.
Brown the Chicken: Heat the olive oil in a skillet over medium-high heat. Add the seasoned chicken breasts and sear them for 2-3 minutes on each side, or until they're just golden brown. This step adds extra flavor to the dish. Transfer the browned chicken to the crockpot.
Make the Gravy Base: In the same skillet, melt the butter over medium heat. Whisk in the flour and cook for about 1 minute to form a roux, which will thicken the gravy. Gradually add 1 cup of chicken broth, whisking continuously to prevent lumps. Cook until the mixture starts to thicken.
Add Remaining Ingredients: Add the remaining 3 cups of chicken broth, chicken bouillon, the additional 1 teaspoon of garlic powder, onion powder, dried parsley, paprika, dried oregano, and dried thyme. Stir to combine all the ingredients well then then pour it over the chicken in the crockpot.
Cook: Cover and cook on low for 5-6 hours or on high for 3-4 hours, until the chicken is tender and cooked through.
Final Gravy Thickening (If Needed): If the gravy needs further thickening, mix cornstarch with an equal amount of water to create a slurry. Stir this into the crockpot, and cook on high for an additional 15-20 minutes or until the gravy reaches your desired consistency.
Serving: Carefully remove the chicken from the crockpot and shred it with two forks. Return the shredded chicken to the crockpot and stir into the gravy. Taste and adjust the seasoning if necessary.