As mentioned in my post "Frills - Definitely a Learning Curve" I've posted below my tip on how to manage a curved hem/seam - in this case a patch pocket.
Firstly, stitch around the edge of the curve you wish to hem, about 5/8" of an inch from the edge. I've sewn this one in a darker colour to be able to see the stitching. I've also used the longest stitch length.
The press the curve in following the stitch line (I did a lot of this for my plum coloured frilled dress!)
Tip: This fabric pressed easily but if you have fabric that's a little more difficult and you need to use steam, wear a rubber glove to stop your finger getting burned.
You should end up with an nice flowing curve
If necessary the thread can be removed (easier if you've used a longer stitch length) if it's showing after being sewn.