In minecraft how do I make a dispenser room?

I want to make a dispenser room for my mini games world and for example I want the whole floor, walls but not the ceiling covered with dispensers. I understand if I can't place it everywhere but mostly covered should do the trick. Also I don't want the dispensers to go on all at once if it could be a time lapse contraption that activates one by one every few seconds please add that down there too. Just so you could probably get a better view(no pic) I'm making a room and the ceiling is wood but on top of the wood is a layer of sand also the floor is covered with lava so the dispensers will be under that but the dispensers on the floor are supposed to burn the wood ceiling and the dispensers on the wall are suppose to hurt the players that are in there