Show canned hints
After solving some clues, you'll want to connect the words somehow. Horizontal connections work differently from vertical connections.
If two words are connected horizontally, they should form a common two-word phrase or compound noun. If two words are connected vertically, they differ by exactly one letter (as in a word ladder).
When you successfully put together the pieces in each section, you'll get the shape of a letter but with one piece missing (the connections between pieces are sometimes needed to disambiguate the letter, e.g. A vs R). You can always deduce the missing word from the two adjacent words and connections.
Arrange the 20 missing pieces into a big loop, where horizontal and vertical connections should work the same way as the rest of the puzzle.
If you read the letter shapes in order of the loop, you will get four 4-letter words separated by Xs. The answer is the word that can go in the middle (i.e. it makes two-word phrases with the words to the left and right, and is one letter off from the words to the top and bottom).