Whatever vegetables you want to cook with your slow cooker turkey, put them in the crock first to literally support the turkey and keep it from sitting on the bottom of the pot. Not using the order of veggies first, turkey second, is a common slow-cooker Christmas dinner disaster.
It's a huge mistake to slow cook the turkey on the bottom because it can stick to the cooker and both the vegetables and poultry are likely not to cook properly at all.
Before you add your turkey on top of the veggies in your slow cooker, be sure to rinse the bird and pat it dry, then rub it down with a seasoning mixture. Look for a seasoning mix recipe that will add some color to your slow cooker turkey since this cooking method doesn't as easily brown the bird as much as the conventional oven method.
Drying your turkey really well with paper towels before adding your spice rub to the skin is crucial since it will help the skin become the brownest and crispiest it can get in a slow cooker. Having the turkey placed on top of the vegetables also helps accomplish this.
After your turkey is all dried and rubbed with seasoning and you have placed it on top of your cut-up veggies, it's important you keep the slow cooker lid on tight for the entire 6-8 hours or so of cooking time. Really, even a few lid lifts to "check" on the turkey in the slow cooker can ruin how well it cooks.
If you're so bored you find yourself wanting to keep lifting the slow cooker cover to look at your turkey cooking, you can always use the empty cardboard rolls from all the paper towels you used to dry the turkey with to make ridiculous seasonal crafts.
After your turkey is cooked in the slow cooker, you can reach maximum browning and crispiness of the skin by placing it under the oven broiler for a few minutes. Of course, watch it carefully so it doesn't burn and your Christmas dinner made with the bird on the top of the vegetables should be a great success!