The shortest useful sleep habit is a fixed wake time. Pick one. Use it every day.
Bedtime tends to drift. Wake time can be held steady with an alarm, which makes it the easier anchor of the two.
Start with the time you already get up most weekdays. Round it to something plain. Keep it for a week before judging it.
When you rise at the same hour, the body has one clear signal to organize around. The morning gets simpler. So does the evening.
You do not need a perfect bedtime to begin. Hold the wake time first, and watch what the rest of the schedule does on its own.
If you keep waking exhausted no matter the hour, that is worth raising with a qualified healthcare professional. A wake anchor is a habit, not a treatment.