This solver tries to find 4 words to solve Letter Boxed (though admittedly this screenshot shows solving the puzzle in 3).
After loading the file with [letter_boxed]., use solution/2. For the puzzle shown above, you would write:
solution([['a','x','n'], ['o','h','l'], ['e','m','i'], ['t','y','p']], Words).
The letters have to be entered lower-case. Sorry. Also the order that you enter the sides and the letters within those sides does not matter.