Well, some of you were and I've just made such pockets again (again on a robe, this time one for myself), so here it is.
This is a patch pocket without topstitching. You can only use this technique if one pocket edge is in a seam and you attach the pocket to the body of the garment by stitching from the inside.
Press the facings to the inside. For a normal patch pocket, you would sew the facing to the pocket with the right sides together, to get a neat corner. Don't do that now.
Press the seam allowances to the inside. It's easier to make this pocket if you use a seam allowance of only 1 cm on these edges.
Now, you can position the pocket on the garment front. Of course, it is practical to have the position marked from the start.
Pin down the seam allowance at the top edge and the corner.
Turn the pocket over and pin its side seam allowance down further.
Sew from the top edge along the cease you pressed in. Don't stitch past your pin in the corner and make sure to stitch the bit curve before it in the direction it will need to go in.
Turn the pocket right side up again.
Now, you can pin the bottom edge.
Stitch from the open side to the corner along the crease. To do this, you have to kind of bunch up the pocket and move it along while you sew. It may take some stopping sewing, putting the needle down and adjusting the fabric around it. You should be able to stitch all the way up to the end of the line of stitching you made before. If you can't, don't panic. You could cheat by closing the remaining gap with some hand stitches.
And that's your pocket. No visible stitching on the outside of the garment.
It's all here, on the inside.
Then, you sew the side seam, which closes the other side of the pocket. My robe has an A-line shape, which is why this side is at an angle.
In a plain, slightly fluffy and sort of stable-yet-pliable fabric like this one, this pocket isn't particularly difficult to make. The real test with these is, predictably, making them in plaid or stripes. And I wouldn't recommend slippery fabrics, like satin (although I wouldn't recommend those for regular patch pockets either).
I prefer this type of pocket over regular patch pockets any day (for things like coats and robes. Not for the back pockets on jeans, of course). They don't have any real structural advantage but I just don't like topstitching if I can avoid it.
It's the sort of detail a non-sewer would't even recognize but which makes a nice subtle proof of skill to those-in-the-know.