It seems like you don't want a game with predetermined words that have to be found - but instead a game with completely random letters and the user has to find any words that occur. It sounds a lot like the game
Boggle. If this is the case, then you don't need to write/load a text file for the game board, but can instead just randomly generate 16 letters.
That would be the easy part. The difficult part would be validating all the words that the user enters; (1) Find out if the string of letters actually occurs on the board, then (2) determining if it's a real word.