I made one of these with my sister. It was a lot of fun, and we didn't worry about the knots laying flat. We just tied. I have no idea about a hidden knot in the corner. Maybe you are worrying too much.

If you're concerned about the fringes not laying flat, try tie'ing the knots the same direction. It will give a more uniform look. Over-under/over-under. It may just be that the knots are being tied differently and it's the uniform look, not the laying flat look that has you bugged.

...at least, that's how I've always tied mine. Hope this helps! :)

Thanks for your imput ladies. I practiced a few times and seem to have mastered a flat knot. The over/under worked OK. The blanket has turned out rather well. I hope my grandson is as pleased with it as his Nana is.

I do "over- under, under-over" that way the colors alternate.

When I have done these blankets I tied every second knot on one side, turned the blanket over and tied the remaining knots. On the corners I crisscrossed the srtrips so that one strip came from one side of the corner and the other strip came from the next side I was going to work on.