Don't stress too much about lining the bandanas up perfectly or matching up corners, because this will not happen! Bandanas are never cut straight! You have a couple of options: Just deal with it, that is just part of sewing with bandanas. You can make small adjustments when sewing to help keep them straight. Another option would be to press the bandanas, stack them together, use a rotary cutter and mat, and cut them into perfect squares.