Guitar Case Humidifier - Build Your Own - Inexpensive

How to build your own acoustic guitar (any instrument) case humidifier. I used to put sponges in Plastic Travel Soap Dishes and drill holes in the lid, but they tend to roll and knock about the case which could scratch the headstock. This is so simple and available very inexpensively. Parts are sponges from a dollar store (6 for a buck) and a ziplock bag - either a regular or freezer. I tear/cut out the top seal edges so nothing can be sealed in. Then I roll up the bag and cut slits in it so there are 4 or 5 rows of slits on each side. Wet and wring out the sponges, and then pat them dry and stick them in the bag. Place it under the headstock area of the case for guitars.