This puzzle is made to train kids about the different representations of numbers from 1 to 5.
I use it for my pupils (6 years old)

First, engrave the front side without the circles.
When finished, remove the pieces but leave the frame in exactly the same place.
Then engrave only the circles.
Remove all the wood and put another board for the back
Engrave the back.
Glue the frame of the front part on the back board.