Bring the buckwheat and stock to the boil in a pan. Cover and simmer over a low heat for approx. 15 mins.; do not remove the lid. Leave the buckwheat to cool.
Mix the vegetables and oil in a bowl, spread on a baking tray lined with baking paper.
Bake for approx. 15 mins. in the centre of an oven preheated to 200°C. Remove from the oven, season with herb salt. Mix in the buckwheat, oil and lime juice, season again with herb salt as required. Scatter the feta on top. Mix in the basil and spinach prior to serving.