Use the EU261 claim form on the SAS website (haven't had to use it for a while, but assuming it's still there). It's pretty effective and guide you through submitting all relevant information.
Vouchers are often not used when a short haul flight is diverted back to org. airport and next flight is within 2 hours. But as previous posts has stated, you can claim reasonable food expenses together with the EU261. I recently had a 2,5 hour delay, on a flight back from PRG, where they accepted to refund my additional parking and PRG lounge fee instead of restaurants expenses.