Mix the flour, salt, sugar and yeast in a bowl. Pour in the water and oil, mix and knead to form a soft, smooth dough, mixing in half the walnut kernels. Cover and leave to rise at room temperature for approx. 1 1/2 hrs. until doubled in size.
Shape the dough into a loaf approx. 30 cm long and coat with the remaining walnut kernels. Transfer the bread to a baking tray lined with baking paper and, using a knife, make around 5 incisions on both sides, approx. 2 cm deep.
For approx. 35 mins. in the centre of an oven preheated to 180°C. Remove from the oven, allow to cool on a cooling rack.