If they are not fire bricks. They will break. Im not sure if you are trying to use the kettle as a dutch oven? Or using it to cook with a dutch oven? Cooking with dutch oven in a traditional way is skill all guy's need to learn. You can just run your grill up to desired temp and slam the oven on the grate indirect and get the same results as trying what the pic shows. Or learn the art of dutch cooking.
Most baking recipes require a temperature setting of 325ºF. An easy method to get a temperature of 325ºFahrenheit within your Dutch oven is to subtract or add the number 3 to the size of your Dutch oven to determine the number of charcoal briquettes to use underneath and on top. Find the size of the Dutch oven you use (see chart below) to know the correct number of briquettes.
Dutch Oven 325° Temperature — Briquette Quantities
Size of Oven Top Bottom
8-inch 11 5
10-inch 13 7
12-inch 15 9
14-inch 17 11
16-inch 19 13
The following example uses the formula for a 12-inch Dutch oven.
* Subtract 3 from 12, which equals 9 — the number of briquettes to place beneath the oven.
* Take the number 12 and add 3, which equals 15 — the number of briquettes to place on the lid of the oven.
With this formula, 9 briquettes go underneath and 15 briquettes are placed on the top of the lid of a 12-inch Dutch oven to cook at 325ºF. One-third of the heat will be underneath the Dutch oven, and two-thirds of the heat will be on top. Heat rises, so you do not need as many coals on the bottom of the oven.
Arrange briquettes so they are evenly spaced under the Dutch oven and on its lid. Also, you always need to rotate your Dutch oven a quarter turn every 15 minutes to avoid hot spots. Replace briquettes with new coals as they burn out.