One way to cook turkey in a slow cooker is to thaw a boneless turkey roast, and put it flat, skin-side up in a cooker that is 8 inches in diameter. Cook the turkey on low for four to seven hours until the internal temperature is 170 F.
To thaw the turkey, put it unopened on a tray in the refrigerator for 1 1/2 to two days. If quicker thawing is necessary, put the unopened roast in cold water for three to five hours. Refresh the water every half hour to keep the turkey cold.
Cook the turkey in the slow cooker within four days of its thawing. Take off the plastic netting and package, but leave any string netting on. Adjust the position of the netting to make later removal of the turkey from the slow cooker easier. Drain the juices, and use paper towels to gently pat the turkey. Spray nonstick spray on the turkey, and insert the turkey into the slow cooker.
Pour half a cup of water over the turkey, and check the center temperature of the turkey after four hours. Also check at the ends and near the top of the turkey. The temperature should be 140 F by four hours.