Puzzles/Subdivisions/Subdividing a cornerstone/Solution

Subdividing a cornerstone Solution

Think of every square as a combination of 4 smaller squares like this one

 -- --
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 -- --  
|  |  |
 -- -- -- --
|  |  |  |  |
 -- -- -- -- 
|  |  |  |  |
 -- -- -- --

This piece have 12 pieces so every identical piece must have 3 small squares.

Then the solution is

 -- --
|     |
    --  
|  |  |
 --    -- --
|  |     |  |
    -- --  
|     |     |
 -- -- -- --