would be good for boxes too Making Felt Bowls . "While it is simple for anyone to make a felted bowl, it is challenging to make one well." quoting Maria Roth, the author of linked article and maker of these bowls
Secret to Cutting Felt Freezer Paper! Trace your pattern, picture, whatever you want to cut onto the paper. Iron it onto the felt until it stays. Cut around your pattern and then peel off the freezer paper.