Really fun, done mostly 3x3s (a couple 4x4s) but have yet to figure out how to swap two adjacent letters. Keep getting stuck right at the end on some!
What you want to do is find what I call a "donor letter".
Say you have:
BOAR UPTO MUTT PSSA
Where you want to swap the last SA to make PSAS.
What you'll want to do here is find a 'donor letter' of either S or A. In this case we have the A of BOAR. You'll put the BOAR's A in the place you want the A in PSAS, in this case the third slot. Then put the S that is now floating down into the last slot of PSAS.
I understand that this is probably a bit headache inducing to read, so I recorded a clip! https://youtube.com/shorts/SqGgcPXevE4
Thank you for playing by the way!