Sleep enough. Most people do not get 8 hours, even with naps. Feeling rested is important and getting yourself in the delta wavelength of sleep is helpful for flow.
One of the suggestions was to take some time and make goals every single day, at the end of your work day. Prepare for tomorrow, so that you don't lose your place. One method is to use your early energy to do the hardest, and least rewarding task. That way, when it is done, it is all good from there. If you cannot finish your list today, do it tomorrow.
Gratitude practice every day is recommended for getting yourself into flow. Do at least a few minutes. Not sure what to be thankful for? Start saying "Thank you," over and over and watch how things come to mind.
Imagine waking up and doing 20 minutes of mindfulness. Being in the moment and setting up that pattern for success today...
Read a book outside your niche, outside your area of mastery. 25 minutes a day is the recommendation. Your brain makes connections all the time. Give it raw information from a book that is related to your field and watch your brain start to connect the dots.
For today, we will end with suggesting that you do something that really excites you, every week. What already gets you in flow and push yourself to have fun and passion, push it by challenging yourself. Not too easy, not too hard as you seek out novelty, complexity and unpredictability.