A reader asked me about this pattern. It can be found in Florencia Campos Correa’s book, 100 Pin Loom Squares (under a different name), but if you don’t own that book, her three-layer patterns, and many others, can be found in the vintage Weave-It Weaves, Weave-It Magic Squares, Loomette Handbook, and Original Loomette Weaves handbooks on eloomanation.
It hardly seems possible, but apparently I’ve never woven this one. I think the diagram will give you a good idea what the finished square will look like.
There are some similar patterns in this post.