First, a quirky fact: a frozen turkey crown is basically a solid ice brick. Do not try to cook it from frozen. That’s a recipe for a cold heart and a burnt outside. You need to thaw it in the fridge.
Plan 24 hours for every 2kg (4.4lbs) of crown. Forget this, and you’ll be googling “how to defrost turkey in a hurry” at 3 a.m. Spoiler: it’s not fun.