I’m not sure if it makes sense to try to find a “scientifically proven” technique if all you want is something that works for you. What works for a large group

I’m not sure if it makes sense to try to find a “scientifically proven” technique if all you want is something that works for you. What works for a large group of people in a controlled scientific study does not necessarily work for each individual in that study, let alone for you. You could do a scientific study on yourself, though. Figure out some objective way to measure your own concentration, and then try various interventions one at a time to see which intervention correlates with the best concentration. You could also try combinations of interventions—having a beer while taking a shower?—to see if you can get an even stronger effect. I’ve never done such an experiment on myself, as planning and implementing the experiment would distract me so much that I wouldn’t be able to concentrate. So I just exercise for a while every morning. That seems to work—for me.