This puzzle has two identical pieces that lock into each other in a cross pattern and the challenge is to separate between them.

You will need four metal pins with 4mm diameter and 35mm length such as the ones here https://www.aliexpress.com/item/32868697789.html

Set your slicer to pause just at the top of the horizontal cavities so you can place the two pins before you continue printing.

Printing is straight forward, e.g. PLA, 0.2mm layer, 3 shell layers, and 15% infill. No material support.

After printing I clean the through holes by drilling them with a 3/16 drill bit. This makes sure that the pins go smoothly throughout the holes.

The Fusion 360 design file is included.