I am not sure about the "sewn all around" part of your question. I usually start with a block and a diagonal line and sew two HST (half square triangle units) which I then cut again and reassemble. Am going to assume your 6.5" includes your seam allowance for a 6" square.
Here's Jenny Doan/Missouri Star quilt company video
https://www.youtube.com/watch?v=uIyH...l=MissouriStar
And here's a text non-Jenny version
https://www.diaryofaquilter.com/hour...lock-tutorial/
For me, I typically cut large and trim down and would use finished size + 1.5 inches or 7.5" starter blocks for your (finished) 6" 9-patches. Here's yet another website with a chart! This quilter is a bit more precise than I am and uses 1.25 instead of my 1.5.
https://www.scrapish.com/hourglass-quilt-block.html
Hope this helps and is not just more confusing than you started!