Once you become a more confident sewer, you can start to add things that may not be included in the pattern.
A flap to a patch pocket is one such thing.
It's very easy to create a template from your pocket pattern for this add on.
Making your template.
Using your existing pocket pattern, match width and point if it has one.
Take a guess at how deep you want the flap. But remember you need to allow for seams.
Cut 2 pieces of fabric using your template.
Right side together, sew using a small seam allowance.
Leave top edge open.
Turn your flap in the right way and top stitch to match your pocket (excuse my wonkiness!).
If you were wanting to add a button hole then this is the time to do it.
Place flap on your fabric above the pocket - right sides together with the point facing upward.
Fold flap back over and sew a top stitch row across the front to hold flap in place.
You are done.
I added a snap fastener to my flap as a closer.