This is adapted from a recipe I found online several years ago, having repeatedly tried and failed to make really good flapjacks. Buying most of the ingredients from a refill shop makes them almost packaging-free and if you're trying to cut down on ultra-processed food they are good with a cup of tea in place of a biscuit.
The original recipe uses all butter but I normally use a mix of butter and vegan block in varying proportions depending on what is in the fridge, and have made a vegan version with good results.
175 grams butter/vegan block
125 grams sugar - ideally soft brown sugar but demerara is also fine
2 tablespoons golden syrup (measuring golden syrup with a spoon is a messy business but it doesn't need to be too precise)
250 grams oats - NOT jumbo oats. If jumbo oats is all you've got, spend a bit of time crumbling them up smaller, it does affect the result.
Pinch of salt
Sprinkle of ground ginger (about 1/8 teaspoon if you need a measurement but see how much you like)
To these I usually add a good handful of sultanas (or raisins or currants), a few chopped dried apricots, and a handful of mixed seeds. I have also added chopped nuts, dried cranberries and chocolate chips depending on what I happen to have lying around.
Start by melting the fat, sugar and syrup in a large saucepan on a medium heat until the fat has melted and sugar dissolved. Turn off the heat and stir in the rest of the ingredients. It will seem too dry initially but keep stirring and it will come together.
Tip the mixture into a shallow 30cm/12 in x 22cm/9 in baking tray, lined with baking paper. Lining is important but if you are careful and frugal, the paper can be washed and reused several times.
Spread the mixture out evenly with the back of a spoon and bake at 180 deg C/350 deg F/gas mark 4 for about 15 minutes (depending on your oven) until it's a nice golden colour.
Cool in the tin until just warm, then slide out on to a board and cut into quadrilaterals of the size you like to eat. Cutting it is easiest if you place the knife on the flapjack and press down (possibly obvious to some but it took me a while...). It keeps for ages and can be frozen if necessary. I always make two trays at a time as this is very popular in my house.