First look up how to trim a brisket on YouTube then make sure to score the bottom or the fat on the bottom 1 inch or so with a checkered pattern.
Pick a marinade and if you want the smoke flavor (like you smoked it) get some liquid smoke and only put like 2-3 drops in the marinade you like. Marinade it over night, flipping it every hour or so until you go to bed.
Get a baking bag so it won’t be dry and it holds in the marinade, so less mess.
Now take it out of the marinade bag and put it within the baking bag while on a cookie sheet with the scored side up, seal via bag directions.
Now put oven for 250F and cook it until the internal temp is 195F.
Pull it out, don’t cut the bag, open it.
Let it rest while the bag open for 30 mins, after the time you can pull it out and slice it however thick you want it.
If you want BBQ sauce with it, take the drained bag and put how many slices you want with it, pour in the bag your BBQ sauce of choice, close the bag up at the same temp for 20 mins.
Or if you don’t like BBQ sauce just slice it how you like and use some of the juice from the bag to drizzle it over the meat if its dry and then serve.
Times may vary by size of brisket.
Please DM so I can give you a better time based off of your size of brisket.