Here's what I did...
Green-ness: 3/5 for using polystyrene one of the most evil plastics but 5/5 for using it each year even if its not pristine and covered in possum pee!
Frugal-ness: It was free so 5/5 for frugalness
Time cost: About 10 minutes to cut and fit.
Skill level: That which is needed to use a sharp knife.
Fun -ness: Making sure your bees are nice and warm and making lots of honey is very fun!