Yup. Take a chuck of scrap plywood. Cut a peice 12″ by 12″ square. Then take a roto zip or whatever and make a slot to the center of your square. Then in the middle take a 1″ paddle bit and make a hole. I have even added a little spray foam to insulate the cover for the hole.
This works pretty good to keep the hole from freezing and keeps the hole dark. I think that helps.
When you put your flag down it will be sititng on top of the plywood. Works pretty god when you get a flag. Just lift the whole works up and start fighting……..