I always found that if they were left in the oven a bit too long and were like concrete, you just needed to leave them in a tin for a day or two.

2oz butter or block marg (doesn't work well with soft spread, or low fat)

1 rounded tablespoon golden syrup

1oz soft brown sugar (works perfectly well with plain granulated sugar)

4oz rolled oats

a pinch of salt.

mixture fits a 7" sponge cake tin. Gas mark 4, 350 degrees F for 20 minutes.

I always used to bake it on a well greased  and floured foil plate (placed on a metal baking sheet). Because the foil plate was flexible it was easy to get the flapjack off on the rare occasion that it stuck

Sorry, it is a very old recipe - goes back to 1977.