Square format can be so interesting to work with. Some painters find themselves in it, some don't ...
Once someone told me it's not so easy to work in it, but personally never had problem with square shapes. More to say it's my favorite, especially in matter of watercolors and subjects of forest and trees.
Also favorite size of square works for me is 30x30cm.
Years ago made several works for group exhibition contest, and only rule they had was that work should be done in 30x30cm size.
Somehow it went easy to me and as time goes by, still working in it.
Here is one example made in watercolor.
First made square of water on paper and let color do it's job...Something similar to process described here
https://steemit.com/art/@jungwatercolor/sea-salt-watercolor-usage-step-by-step
After paper dried, painted trees in similar manner..
Watercolor technique is easy to learn while you are playing with paper and color.
You need to bee free and be ready to make mistakes and be ready some of those mistakes will end up in garbage :)
Hope some of you will try out in this technique or just make fun with playing with it.