Focus Time for Teachers

I’m sure you get this question a lot from teachers, but I didn’t find it in the search I did.  As a high school teacher with a pre-determined schedule, do you have any suggestions for how to schedule “focus time”? My bigger projects that often require creativity and concentration are lesson planning and essay grading. I only have 1 day a week where I can sit in quiet, without distractions for 2 hours. I sometimes have two 45 minute blocks, but never at the same time of day.  Any suggestions on how to modify the “2 hours focus time everyday” to fit within the framework I’m given?