Become an Expert Instead of a Planner
To be able to become an expert, we need the freedom to make our own decisions and all the necessary mistakes that help us learn. Like bicycling, it can only be learned by doing it.
Experts have acquired enough experience in various situations to be able to rely on their intuition to know what to do in which kind of situation. Their decisions in complex situations are explicitly not made by long rational-analytical considerations, but rather come from the gut.
Chess players seem to think less than beginners. Rather, they see patterns and let themeselves be guided by their experience from the past rather than attempt to calculate turns far into the future.
The workflow around the slip-box is not a prescription that tells you what to do at what stage of writing. On the contrary: It gives you a structure of clearly separable tasks, which can be completed with reasonable time and provides you with instant feedback through interconnected writing tasks. It allows you to become better by giving you the opportunity for deliberate practice. The more experience you gain, the more you will be able to rely on your intuition to tell you what to do next.