The depth that you should place your dead stick will depend on the specific conditions on the day and the water. Some people will tend to fish around 2 to 3 feet from the bottom of the water, and this is where you will find a lot of fish.
Something that can come in handy here is using multiple rods, as you can set them all at different heights to see what works best for the specific conditions that you are fishing in. If you find that there is a pattern, you know where the best place to set up your dead stick will be.
Ultimately, there are lots of different methods that you can use when it comes to setting up your own dead stick, and it is all about finding out which one works best for you. You might even find that different setups work better in different environments, and trial and error is key here.