Every pole barn starts the same way: string, stakes, and a lot of measuring. If the diagonals match, the building is square. If they don’t, every truss and sheet of steel after this point will tell you about it.
The ground up north is full of rocks, so the auger did about half the work and a digging bar did the rest.
Action items
Measure the diagonals three times. Fixing a crooked post now takes an hour; later it takes a weekend.