There are lots of different ways to do this. The important thing for anyone wanting to get started is just to get started and not get hung up on which one you're doing. Box breathing, Wim Hof method, etc, are all great and any breathwork is better than none. For an intro to the topic, James Nestor's Breath is excellent.
Every time I try breathwork (be it box or x-y-z) I feel that the intervals are too long - by the time I finish breathing out my brain goes into panic mode and the next breath is not enough to compensate. I find them the exact opposite of relaxing.
In other words: Lowering your CO2 sensitivity and learning to breathe slowly by doing breathwork is a skill worth acquiring. Your brain going into panic mode in a comparatively relaxed breathing mode could be an indication that your CO2 sensitivity is rather high.