Heat deflectors:
While I do make them, I haven't personally used a heat deflector in my grills for more than 12 years because I believe they increase airflow. (It’s easier to supply them than to educate the ex-glazed pot users to believe they don’t need them) In the glaze ceramic pot, big green egg, Kamado Joe world having a plate with thermal mass inside your grill will give additional stability during ambient temperature changes. Because my grill is so well insulated.. they are not necessary.
I simply preheat the grill empty and then put a piece of aluminum foil on the lower grate for the area I want indirect, put my drip pan on top of that and use them to create indirect airflow. This will give you better performance/less airflow.
https://komodokamadoforum.com/topic/10026-heat-deflectors-in-the-kk/?tab=comments#comment-121321