Im stuck on answer 15 of this puzzle can someone help please?

Top shape looks like this
_ _
|_|_|
|_|

Directly below along far edge is mirror image
_
_|_|
|_|_|

Directly to the right of this along the far edge is the mirror image of that
_
|_|_
|_|_|

Last but not least in the middle this should leave you with the same shape as 2 above:
_
_|_|
|_|_|

Overall it then fits together like this
_ _ _ _
_ |_|_| _|_|_| |_| _
|_|_| |_|_|_|_| _|_|
|_|_|_|_| <-- |_|_|
_
|_|_
|_|_|

OK - clearly answering like I did does not work! Top shape is a "L" rotated 180 degrees anti-clockwise
In bottom RH corner is mirror image of "L"
In bottom LH corner is "L"
In middle there is then a remaining mirror image of "L"

Hopefully clearer this time!