Preheat oven to 350
In your 9x13 pan, place your thawed chicken top side down, (Breast Side Down).
Mix together ketchup, vinegar, sugar, soy sauce, garlic salt, and mustard.
Pour over the chicken.
Bake at 350 for 45 mins to an hour
Turn chicken over and bake for another 30 mins and use your basting spoon to bast the chicken.
Bake for another 15 mins.
Use your meat thermometer and check temperature, it should be 165 degrees.
Remove from the oven and allow to rest for 10 minutes before carving.
Enjoy!