Mix the flour, sugar and salt in a bowl. Add the butter and rub together using your hands to form an even, crumbly mixture. Pour in the water, mix quickly to create a soft dough (do not knead), cover and refrigerate for approx. 30 mins. Roll out the dough on a sheet of baking paper (approx. 30 cm in diameter), place on a baking tray.
Spread the almonds and then the oranges on top of the pastry, leaving a border of approx. 4 cm all the way around. Fold the edges inwards, brush with water and sprinkle with sugar.
Approx. 45 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, allow the galette to cool slightly. Combine the jam and coriander seeds, carefully brush the warm orange slices with the jam.