Heat the olive oil and fry the sausages until lightly browned, but not fully cooked. (Use the searing function of your slow cooker - if you don't have one, use a frypan on the stove then transfer everything to the bowl of the slow cooker at the end of step 2).
½ tbsp olive oil, 8 thick beef sausages
Add the onion and carrots to the sausages, and continue to fry until they start to soften slightly.
1 brown onion, 2 carrots
Then add the remaining ingredients.
800 g finely chopped tinned tomatoes, ¼ tsp cumin, ½ tsp garlic powder, ½ tsp sweet paprika, 1 tsp worcestershire sauce, 1 beef stock cube, ¼ tsp cooking salt, ¼ tsp freshly ground black pepper
Give everything a good stir and pop the lid on the slow cooker.
Cook on high for 6 hours or low for 8 hours.
Serve the sausages whole or sliced into chunks, topped with the tomato sauce.