Pixel owners are free to set the crossword puzzle on their area and set reward for visitors (they pay for the reward and some percentages as the fee).
Select 1 segment (in a row or col) on the map.
Click word button to open word input dialog.
Input each character of the word and click save to set it on the map.
To prevent front-running (idea from Near crossword tutorial)
Words solution is used as the source to derive a deterministic winning (private, public) keys pair.
Derive substrate account from the public key.
The calculated solution is saved into the Blockchain along with creating the puzzle.
Gameplay reference