Slow cooker lamb stew

Name: Slow cooker lamb stew
Ingredients: 700g/1lb 9oz lamb neck fillet, cut into roughly 4cm/1½in chunks; 1 tbsp sunflower oil; 1 large onion, thinly sliced; 25g/1oz plain flour; 400ml/14fl oz hot lamb stock, made with 1 lamb stock cube; 2 tbsp tomato purée; 2 tbsp Worcestershire sauce; ½ tsp dried thyme or 3–4 fresh thyme sprigs; 1 tsp dried mint; 3–4 large carrots (around 500g/1lb 2oz carrots), peeled and cut into 1cm diagonal slices; 500g/1lb 2oz new potatoes, halved or quartered if large (aim for 3–4cm/1¼in–1½in pieces); 150g/5½oz frozen peas; salt and freshly ground black pepper