The borders on the pieces obscure the edge details that you need to help match the pieces up. Often there were pieces with letters that looked like they were needed another piece to complete them but actually they were whole but the border covered the edges.
It would also be nice if I could position pieces freely outside of the board so I could test out potential matches.
In the end, it became easier to just keep trying to place pieces on the board until they stuck together automatically.
That would make it very easy and less about the words. They gave you a whole day to finish it for a reason.
I was baffled by this because the rightmost square didn’t seem to have any pieces where the letter would fit vertically — the unplaced pieces had a border which made it impossible to see which might.