Re Unclued. The grid can be worked out by knowing all the words are 6 letters long. And has 90 degree symmetry (can rotate grid 90degrees and blocks still look the same). We know 12 is a real word and must be down so that gives us 8 blocks straight away. We know where 6 is, so 1 to 5 must be to the left of this, and are likley to be downs (I have never seen a crossword with an across or a down answer in the periphery of a grid where there is a quote or equivalent running around the outside). Rules of construction state there cannot be two unchecked squares in a row. So the 1 to 5 must be spread out fairly evenly, With one at second square in. 5 and 7 must surround the 6. There is only one doubled clue, number 24. And it does not take much logic to work out this has to be in bottom right of cross in centre. From there All of the grid can be constructed apart from one ambiguity in column 5, where the starting point of 9 or 11, depending on which construct you have, is unknown. All the rest do not work with the known location of 6,12 and 24. Nearly all can be done without solving a single clue.
Simon