Cook the kumara and raisins in a saucepan of simmering salted water for 15-20 minutes until soft. Drain well and roughly crush with a fork. Add the garlic, harissa paste or chilli sauce, cumin, ginger, cinnamon, sugar, vinegar, salt and mix well. Gradually stir in the olive oil, then set aside to cool while you grill the bread.
Preheat the grill to medium-high.
Carefully open up each flatbread to make 2 rounds, then grill in batches until crisp and golden. When cool enough to handle, break into large shards.
Drizzle the kumara with a little extra olive oil, dust with paprika or sumac, and scatter with coriander leaves.
Serve the spiced kumara dip on a platter with the crisp flatbread.