Does the snow and cold wind get into your crocs when you venture outside?  Coverup those side vents by pressing in these plugs!

My foot kept pushing one of them out (the last one on the outside), so I made another “tall” version with a taller inner side to help retain it better.  This appears to have solved the problem for me.

While I printed a couple without any type of support initially, ultimately I found that I needed to use a brim.  I didn't think to try turning the model on its face though, so if you don't want to use a brim then that might be worth a try.