The other day I saw a posting by someone who made one of these from a couple of 2×4.
It looked interesting so I did a quick Google and came up with free plans for this "Knot Burr Puzzle" on Craftsman Space.
The plans were in metric. I did not bother to convert and switched my brain out of imperial measurements. That was more of a challenge than building the puzzle.
It was fun and quick and made from scrap. This is pretty rough . . . but it works.
Added an Yin Yang feature by staining one piece with earth pigments...Final result:
Without the light the dark is impenetrable. Without the dark the light is incomplete. Together these opposing forces intertwine balancing each other, giving rise to a puzzle that only the wise and patient can understand.
I think I have found some Christmas gifts.