Ok, first, I apologize for my awful pic but I was trying to be quick with it....I hope I don't confuse you more with it.
1) cut out 2 pieces of fabric in the shape you want from the same stencil (one will be the front of the pocket and one will be the back, or inside of the pocket). They don't have to be the same fabric if you want contrast.
2) line them up evenly with the outside of the fabric
(the good side) facing inward
3) sew as such:
4) the red triangles in the pic above are where you'll need to trim. Be careful to NOT cut into the seam you created. Removing this fabric will help the curve lay flat. Also, trim a bit off of the peak so you don't have so much fabric bunched in there...it will define that point later on.
5) turn the pocket right side out using the opening at the bottom.
6) flatten, press, turn in the opened edge and top-stitch it closed.