Hints: Make Your Own Crossword
It’s much easier to make the crossword after placing the black squares in nice locations. It helps if you can divide up the grid into four or five smaller regions which don't need many words crossing between them. Smaller regions are easier to fill with words, and you can assign just one or two of the tougher letters to each region so that you don't have to deal with them all at once.
Stuck on extraction:
If you’ve only submitted one crossword, one way to help figure out what’s going on is to slightly modify it and submit again. As suggested by the puzzle, it will be easier to get the answer if you use more distinct letters.