Here's a document listing out all secret area locations in the Icy Island in version 0.6.X, along with screenshots to visually aid the search and some tips on how to get them. Useful if you're learning the 100% Icy Island 0.6.X speedrun category, or if you're just doing a casual completion of the world.

https://docs.google.com/document/d/1_grSHMQo8fDCDSCeuoZjTnvZVZAGDuv37hff1hVjYrc/edit?usp=sharing