I would like to present, how to print and prepare handy magnetic chess for 3 players. Board is divided into 3 parts (third-boards), so You can put whole set even into your pocket!

You will need:

3D printer (I used Creality Ender-3) and filaments in 3 colors (white, black and for example red)
small cylindrical magnets (4mm dia, 2mm height) - 174 pieces
instant glue for plastic (gel)

Step 1: 3D Print

Print 3 times:

third-board in black
set of squares in white
set of pieces in red, white and black

Put attention not to scale your stl models, because magnets will not match their holes!

Here You will find solid model made in Design Spark:https://www.thingiverse.com/thing:5375892

Step 2: Glue Magnets Into Pieces

Put a drop of glue into hole on bottom surface, install top magnet from stack.

Always keep magnets in stack to not confuse polarity. All pieces have to have magnets in the same polarity.

Step 3: Install Magnets in Squares

Put a bit of glue into the hole in black third-board.
Holding piece from opposite side, insert magnet in hole - magnet will properly orient by itself thanks to proximity of piece. Wait for glue to harden.
Repeat steps 1-2 for all white squares, then glue squares into hollows in third-board

Step 4: Install Side Magnets of Third-board

Install magnets in sides of third-boards in similar way as in step 2. Keep the same polarity in all third- boards: South on left side, North on right side or vice versa, but consistently!