The goal of this puzzle is to make three cubes from the given pieces. The designer of this puzzle is Kohno Ichiro from Japan. Although this puzzle only has three pieces, the solution was pretty challenging for a couple of my test subjects. As for the build, I used scrap wood and purchased magnets. The total material cost was about $1.00 per puzzle. For the non-woodworkers, I've also included STL files for 3D prints.

This video shows the solution

Step 1: Tools/Materials

Tools:

Saw (Table, Miter or Hand)
Drill
3/16" Drill Bit
Ruler
Pencil
Wood clamps

Materials:

Wood: 1" Wide x 7" long x 1/2" thick
Magnets: 5mm diameter x 2mm thick
Wood Glue

Step 2: Blocks

The parts are pretty simple. Cut the 1/2" thick piece of wood into 1" x 1" sections. You will need 6 pieces. I made extras since I usually screw something up during builds.

For the cuts, I used a table saw. A miter or hand saw would work as well.

Step 3: Holes

As with the size of the puzzle, the size of the magnet is somewhat arbitrary. Based on my 1" cubes, I figure 5mm diameter magnets would fit reasonably well. Note that 5mm is approximately 0.197 inches. Since I wanted a press fit, I drilled the holes to 3/16" (.188"). Note that I made two versions of the puzzle. The first was from poplar (softwood) while the second was from walnut (hardwood). The 3/16" hole turned out to make a perfect press fit for the hardwood. For the softwood, I had to add a little epoxy into the hole to guarantee the magnet wouldn't come out.

Step 4: Mark Center for Holes

Using a straight edge, mark lines from corner-to-corner to find the center of the block.

Step 5: Punch and Drill

Use a center punch to aid in drilling. I used a 3/16" bit and drilled the depth per the drawing.

Step 6: Magnet Orientation

Magnet polarity is key to this puzzle. Unfortunately, I'm not going to explain this step very well. I actually built the puzzles with different arrangements and both worked. I used this arrangement on the poplar and 3D print and I'm happy with it.

You will have 3 pieces (A, B & C). Place the parts on a table as shown. The four magnet locations are called out as 1-4. Orient the magnets per the table. Note that "+" or "-" is referenced from the outer side of the block.

Step 7: Magnet Installation

Place the magnet in the hole. Use a wood block or any other hard surface to press the magnet into the hole. I used a small dowel to sink it slightly below the flat surface. If in doubt about the fit, add a little epoxy in the hole before inserting the magnet.

Step 8: Block Assy

I suggest building the puzzle up without gluing the sections together to verify everything will go together. Mark the parts with a sticker as A, B & C. Once you are sure everything goes together, proceed with gluing.

Step 9: 3D Print Files & Solution

All the parts are the same. You will need to print 3 pieces. Two STL files are included. One has a 5mm hole while the other is slightly oversized (5.1mm). If the 5mm is too loose, use a little epoxy before inserting the magnets.

The red, green and yellow show the solution. Note that you might need to shuffle the parts around due to magnet polarity.