We prefer to never cook a flat!
Guys that vend/cater will do it to save people/labor time.
Yield can be as high as 65%,time is shorter,labor is less.
A GREAT quality flat cooks fine,if you have some experience.
The point is what cooks want to eat.
Like GLH says,or paint it with about 2/3 cup Cookshack mild sauce and a little CS brisket rub.
Be sure of what the temp at your RACK is.
Start it at 225*,after foiling kick it up to 250*.
I have had maybe a dozen flats come done as low as 187*,and lots of folks don't cook as many burgers as we cooked briskets.
Take it until it probes like soft butter and let it set in a hot box for two-three hrs.
I'm not advocating foil,for anything except speeding up the timeline-or sometimes lower quality meats,or SEVERAL failures you can't eat .
Smokin' will say to learn the cooker thru experience and take good notes.
Then,you can adjust for anything.