These easy-to-make card and photo holders look great, work well, and would make perfect gifts or products to sell at craft fairs or on Etsy.
The angled 10 degree cut supports even thinner paper that would fall over if the slot were straight. They use a small amount of wood, and can be built with limited tools.
These came about as I was prototyping an idea, and got fascinated with making this curved cut. I found several different ways to do it, and eventually tried making the cut with a jigsaw instead of my band saw to make the project accessible to more woodworkers who may not have a band saw.