This is a variation of the simple, flat, curved patch pocket- it is gathered to give it more volume.
Start out with a scoop-shaped semi-circular piece of fabric for the pocket, and a strip of fabric for binding the top edge - you can use bias tape or a regular piece of fabric. Fold-in seam allowance is included in the curved edge but the top edge has no hem or seam allowance for the top edge - it will be bound by the fabric strip. Finish the curved edge of the main pocket.
Gather the top edge of the pocket using your usual method, for example -
- differential feed by changing the upper and lower thread tensions
- manual gathering by pulling the thread in long stitches or
- using a gathering foot.
With right sides together, sew one edge of the binding strip to the top edge of the pocket. The width of the top edge of the pocket should match the width of the strip.
Press seam flat, fold the binding strip over to the wrong side of the fabric, fold in the seam allowance of the binding and stitch-in-the-ditch on the right side of the pocket to secure.
Here is the wrong side of the pocket, showing the stitches. Doesn't matter if they are visible- it's the inside of the pocket after all.
Actually, I usually sew my bias tape on in the opposite direction - I start on the wrong side of the pocket and end up top-stitching on the right side. I like the visible top-stitching, but many folks like the invisible stitch-in-the-ditch method, so I picked that to demonstrate here.
The pocket is finished. All that remains is to fold in the curved edge, pin in place on the garment, and top-stitch down.