Bake for 60 minutes or until the meringue starts to turn a very pale tan color, then reduce the heat to 250°F and continue to bake for 45 minutes. Turn off the oven (don't open the door), turn on the light in the oven (don't stress if the light doesn't work) and let the meringue sit in the cooling oven for at least an hour, but it can be stored like this over night.
The center of the pavlova will collapse, that's just the nature of the beast and where you will put your filling. The outer edge may crack a touch too, but I've made this shape several times and it generally only cracks a little if you do not open the oven door. The inside should be soft, but not at all wet.
Fillings: I filled my pavlova with whipped cream made with 1 1/2 cups heavy whipping cream, 1-2 tablespoons confectioners sugar, and 1 teaspoon vanilla extract. I topped the cream with 1 cup lemon curd and garnished with berries and passionfruit.