I'd spend the 10 minutes and make one finished 10 Minute block.
The 10" size ends up with an approximately 18" block.
Way too big for what it sounds like what you want.
I would think starting with a 5 inch block would be what you want. I think that will end up about 8 inches.
Make one then press and measure that block. If it is 8" then you need a 1 1/2" border on each side of your photo block.
Add your seam allowance and cut your strips 2" and it should come out 8" finished. This is only a guess as I have not made a 10 minute block yet!
If that is different then just cut your strips for around the photo bigger and plan to cut down to size.
HTH