Cooking a Turkey crown

The idea of cooking a turkey upside down is that the fat from the fattier bits of the bird (the legs etc) runs down into the breast. As a crown has none of these bits, there's no point in cooking it upside down.

By all means butter and bacon it though - turkey breast is very lean so needs all the fat it can get to keep it moist, so use good fatty bacon.

Take it out of the fridge a good hour before you cook it, preheat the oven to 180C, and cook for 20 mins per pound (454g) + 20 mins. Baste regularly, but be aware that every time you open the oven door the heat drops dramatically, so don't be overzealous - once every 20 minutes should be ok. Then let it rest for half an hour, on a warm plate, under foil. This will help with juiciness.

Brine, brine, brine. It's the most important thing you can do to maintain the flavor and moistness of this potentially dry meat. The suggestion above to use a meat thermometer is also vital if you don't want to overcook. The advantage that you have is that you only have the one type of meat (white) to be concerned about, so you can go for the correct temperature without being concerned that the legs and thighs won't be done. And remember that your turkey is going to coast up as it rests, so pull it out of the oven when the temperature is 160 F, not 170, and let it coast up to the final desired temperature. On the topic of temperature, I think 170 (the "safe" temperature that you'll see everywhere) is WAY too high. I actually pull my turkey breast out at about 150. Moist, tender, but slightly pink and that throws some people off.
The basting and larding (laying on of bacon) will add flavor and crispness to the skin, but the biggest benefit will be gained by brining. To recap:

1. Brine your turkey. A cup of salt to a gallon of water, or you can add brown sugar, or you can use vegetable stock, or any of a number of brines that you will find on the internet, but do it. Brine it.
2. If you want crispy skin, dry the turkey after brining and let sit in the refrigerator for a while (hour or more). After that you can butter or lard the skin.
3. Roast with your favorite technique, either starting low and finishing high temperature oven, or start high and finish low, or, my favorite, run it high the whole time. Baste if you must, but more than once is probably a waste of time and oven temperature (every time you open the door, you cool your oven).
4. Use a thermometer. Take it out at 160F (or 150 if you are comfortable with meat that is done less).
5. Let the turkey "rest" a half hour, minimum. Tent it with foil, but let it sit.

Tightly wrapped in foil,sealed. Then 25-30 mins at 200°C/400°F then turn down to 180°C/350°F for 12 mins a kilo (2.2 pounds).

Job done!