Combine paprika, sugar, cumin, fennel seeds, garlic powder and onion salt in a bowl. Rub the mixture all over the turkey. Season with pepper.
Place potatoes in the base of the slow cooker. Pour over 3/4 cup stock. Top with turkey. Cover. Cook on LOW for 6 hours or until juices run clear when the thickest part of the turkey is pierced with a skewer.
Preheat oven to 240C/220C fan-forced. Line a large baking tray with baking paper—transfer the turkey to a plate. Cover loosely with foil to keep warm. Set aside to rest.
Using a slotted spoon, transfer the potatoes to the prepared tray. Cut in half. Roast potatoes, turning, for 20 to 25 minutes or until golden and crisp.
Meanwhile, melt butter in a large frying pan. Add flour. Cook, stirring until the mixture turns golden. Gradually whisk in ½ cup of cooking liquid until combined. Add remaining stock and thyme. Cook, whisking constantly, until the mixture bubbles and thickens.
Slice turkey. Add parsley to potatoes. Toss to combine. Serve turkey with potatoes, gravy and buttered peas.