I saw this on a diy blog, can't remember specifically where though. It's such a no brainer but once I found this out a couple years ago I wish I'd been doing it all along, which is why I'm sharing it!
All you need is your boots and old magazines!
Do you hate when this happens? I do. It causes creases and folds in my boots
Roll up magazine
Place in boot
Keeps your boots standing up and is also nice because it gives a home to my old magazines that I don't want to throw away quite yet. So simple I wish I came up with it on my own.