A visual of your coop would help us out a lot. How big is it? Is it a walk-in coop or a small one? What does the floor and framing look like? How high do you want to raise it?
About anywhere you are going to have to deal with high winds, so the base needs to be able to handle that and you need to firmly fasten your coop to the supports. Depending on how big it is, how high you raise it, and the strength of your coop framing, that may be nothing more than some 2x4 posts fixed in the ground and cut off level, or you may need to use something much more substantial with truss work, which is a fancy way of saying to put in a few diagonals or maybe some horizontals.
If your coop already has a floor, you don’t need any plywood or lumber decking. You just need some supports to fasten it too.
I don’t have a visual that would really show you anything, but for my 4’ x 8’ grow-out coop I repurposed something I already had made with a simple frame of 2x4’s and covered in plywood. It was pretty strong structurally. The soil it was going in was a strong rocky clay. Your soils makes a difference too in how you fix the posts.
I dug holes at the corners about 18” deep with post hole diggers and set the posts on concrete. My posts were treated 2x4’s 4 feet long. I built a frame out of untreated 2x4’s that perfectly matched the bottom of my existing coop and used that to position the posts so that frame could be screwed not the side of the 2x4 posts. When setting the posts I did not worry too much about height, but I took care to get them vertical and spaced right. After the concrete set up, I cut the tops off those 2x4’s so they were level, then screwed that frame into them so it was level. A good level is a good tool to have for something like this.
I set that coop on top of that frame and used strips of plywood to tie the base to the coop. I used 6” wide strips of plywood and screwed them into the 2x4 frame on top of the supports and the bottom 2x4’s of the coop. If you do that on all four sides, it’s not going anywhere. I’ve had 70 mile per hour straight line winds through that area without a problem. My coop was strong enough I really did not need that frame but I built it to line the posts up right so I figured I’s just use it.
Hopefully you will get something useful out of this. Without knowing more about your specific situation I can’t get any more specific than thus. Good luck!