Previously, I wrote about 自由人.
When you understand that 自由 equates to freedom, you will be able to access the beauty of this high-frequency, high-utility idiom: 自由自在. I spotted this idiom pretty often during my stay in Japan. This was seen on the cover of a revision book aimed at junior high school students:
The characters are identical in Chinese and Japanese, so you just need to remember the respective pronunciation for each.
Chinese reading: zì yóu zì zài
Japanese reading: jiyū jizai
So how is this idiom related to the concept of freedom? Well, it means that you are carefree and not bound by restrictions.
In the context of the revision book, using 自由自在 means that you can master the subject in a relaxed and leisurely manner.
Of course, you can say that you are stacking sats in a ziyou zizai manner!