This first pair I made with a random sheet I had laying around to make sure it the size fit, etc. I made them extra long because that's how he likes shorts, although this might have been a little too extra.
I love that they are a flat front, but still elastic in the back for comfort and ease of fit. I even whipped him up a second pair when Cow Appreciation Day rolled around.
I wouldn't recommend telling a 10 year old that you need a picture of the back of the pants - you know..
Anyways, if you need a shorts pattern, this is my go-to: Kid's Shorts. If you've never sewn a pair of shorts, you should. They go together pretty easily and once you make one pair, you'll make the others that much quicker. I know we're rolling into fall, but there are plenty of shorts-wearing days left!