Hi there, good to know that you got this problem. You don't need to release the box you need to carry them to the other 4 boxes and it will automatically place the box. I actually made a new build with hint and green area so that it will be more intuitive .
Viewing post in Welcome To Retail jam comments
Great well I actually left a possibility of accessing the bottle with keys without third box for my self to make gameplay shorter for myself. If you found it out good for you) In terms of how it was intended to be played I posted a video so that the people can see an actual gameplay almost like a speedrun.