u/Tuxxa

Tried this on my players. It's surprisingly hard even though the effort needed to prep isn't that much.

Write a sentence you want to hide in the note. Count the letters. Prepare a X by X -grid that fits the letters. Make sure the sides are equal (change words around a bit to fit them).

Put the first letter in the the right-most column's last row. Second letter on top of it, to the second last row, etc. Basically, write from the bottom to the top, right to left.

Use capital letters, no spaces, use "+" as sentence break.

End product looks like letter mess, in which it may have small accidentally occurring words here and there. Nice red herrings for players to obsess over.

You can leave it to them to solve whenever.