I used to carry a small knife in my watch pocket, but found that I like larger knives more. I then started buying cases to carry the larger jack knife or trapper. I found them acceptable, but at times they would look out of place, such as when I needed to dress up to go somewhere like church, a meeting, etc.
I then started just stitching a small pocket at the back of the right hand pocket of my pants. It separates the rest of the pocket from the knife. It's very easy and works great. Just turn your pocket out, and sew one line of stitches for however wide a knife that you want to carry. The knife slips into the newly sewn pocket easily, and comes out easily. Just push up on the bottom of the knife.
Now I carry any size folder I wish, and it is out of the way, and can't be seen. It's protected, and stays in place. And yet accessible.
It takes me approx. 10 min. to sew a line of stitches into my pocket. Simple like that.