How I created my blackboards (taken from reddit)

1. I designed the boards in Illustrator  then exported them as *.dxf files
2. The CNC router (at my university) cut it according to the dimensions I gave it.
3. The next part was to sand off the sides, as the router leaves 'bridges' when it cuts so that the pieces don't go everywhere while cutting.
4. The material I used for the boards is 9mm MDF and before I continued with painting I coated them with an MDF sealer. The sealer is very thin and water based so any brush will do for the coating and it leaves virtually no visible marks.
5. before I continued with painting the board I used 'chalk board' pens to colour the inside of the letters white (I thought the colour would look better if sprayed on white - I no longer think this was necessary).
6. the spray paints I used for the letters were water based liquitex. After spraying, on some of the boards there was a buildup of paint residue. I filed these down with medium sand paper and smoothed it with a fine sanding paper. here are the results
7. I used simple 'blackboard' black paint for the boards - the only real tip I got was to use a roller so that no marks would be left on the surface and make sure it is the kind with micro fibres (usually they are pink).
8. Finally, when it comes to painting the boards, I painted each side with 3 coats so that the board will not bend. However, because I used the sealer earlier (4) this may not have been necessary, but it looks a lot nicer - it also means you could use both sides to draw on.