Set sous vide machine to 54C/129F.

Season flap steak lightly with salt or a seasoning of your choice. Place meat in sous vide bag and remove the air through a vacuum sealer or the displacement method. Drop the bag in the bath for two hours.

Remove bag from bath. Take steak out of the bag, pat dry with paper towels and season with salt and pepper (or seasoning) to taste.

Heat up large skillet on high and add oil. Sear flap steak for 1 to 2 minutes on each side. Remove from pan, and place on a plate to rest for 5 minutes. Once rested, serve and enjoy! Alternatively sear the beef on a grill or using a searing torch.