We used the same measurement from our 1″x6″ to mark and cut two pieces of 1″x2″ boards. Since we had three windows clustered together to make one large window trim unit. We worked from a 12 foot length board.
Our header had to be very long for our large window, and since we couldn’t find 1″x2″x12′ boards, we had to cut and attach our 1″x2″s in 6 pieces to the longer 1″x6″x12′ board.