I don't have to hunt over ice often here in TX but I read an article just the other day in Waterfowl Hunter Magazine that said to make a 20 yard hole in front and slightly upwind of your blind. It said to jam it full of dekes leaving just enough room for passing birds to drop in. It also said that the dekes should be tightly bunched up and not worry about them bumping together. The reason being, in cold weather, open water is at a premium and ducks naturally bunch up tight.

Good luck and hope the tip works for you.