Link here
http://www.thekitchn.com/how-to-roast-a-turkey-upside-down-237555
Jackdaw you can buy special roasting racks to cook an upside down turkey. Some recipes recommend cutting a ciabatta loaf in half lengthways and use the 2 halfs to support the turkey
I don't bother, you can just wedge it in the rack held by some balls of crunched up cooking foil. Even if you just put it in the oven upside down but 'lopsided' it does not matter. The beast may look a bit 'squashed' but once it is carved no one will be any the wiser except that the meat will be moist and tender.
I have been doing the turkey this way for around 10 years, since I worked in a 'carvery' kitchen for the whole Christmas period. The chefs did all the turkeys upside down all 2 tonnes of them!