An independent creation in OpenSCAD inspired by Angus Deveson's Maker's Muse: Huge 3D Printed Sliding Puzzle! Print in Place "15-Puzzle"
OpenSCAD files are just a text files. You can edit the number of pieces, the gap, and the size of each piece. The file also has a 'slicer' object so you can add a topo-map or any other artwork and difference it with the slicer so the art sits on top of the pieces but not the gap.
For artwork ideas, take a look at some lithopane makers.
You will want to add artwork before printing, because a blank puzzle is pretty boring.
I've included an Australia .stl, rendered with a 0.6mm gap, based on the aus.png grayscale image.
The 2x2 version is so you can dial in your gap setting.
You do need a raft.
My first test, at 0.3 gap was frozen. I tried again at 0.6, and was able to loosen it to move, with difficulty: It took a hobby knife to clean out the grooves, and quite a bit of force, but it works.
OpenSCAD took 15 minutes to render the Australia puzzle. Be patient.