Although this is titled to go with the "3 Cut Block" this technique can & should be used when squaring any piece or blocks.
So here is the block we are starting with from the thread "3 Cut Block - so fun":
http://davesgarden.com/community/forums/t/1143469/
This is what a block will look like before you do any trimming.
Squaring Up "3 Cut Blocks"
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