sorry about the photos, my 7 year old took them...
So you start off with the pants and cut off the length that you want your shorts to be a hem.
Then you cut the extra leg pieces, using a pair of kids shorts as a pattern I cut 2 front short pieces and 2 back short pieces.
Lay them on top of each other, right sides together, and sew the center arch together- I sew twice to make a studier seam since this is what usually pulls apart.
Flip the shorts around so that the center half circle you just sewed are on the front and back of the shorts and sew down the out sides of the shorts. Roll the top over leaving room for your elastic and you're done!
A matching pair of PJ's!