Bring a large pot of water to a boil. Combine the first 9 ingredients in a bowl.
Add the cabbage to the boiling water and cook until firm/tender, about 2 to 3 minutes. Cool in ice-cold water and drain well. Trim off the lower part of the vein running through the centre of each leaf and discard.
Spread half of the sliced onion in your slow cooker. Place a cabbage leaf, curved side down, on a work surface. Set 1/6 of the turkey mixture in the centre. Fold over the sides of the cabbage leaf and then roll tightly. Set in your slow cooker, seam-side-down. Repeat with remaining cabbage and filling. Combine the tomato sauce, stock, honey and vinegar in a bowl. Pour over the cabbage rolls; sprinkle with remaining sliced onions. Cook on the low setting for 8 hours. Serve topped with sauce and sprinkled with almonds.
Note: This recipe is designed for an oval-shaped slow cooker with a 5 litre or more capacity. To toast the almonds, place in a small skillet and set over medium heat. Cook, swirling the pan from time to time, until lightly toasted, about 5 minutes.