If the goose is frozen, thaw in refrigerator. Leave enough time so that it will be completely thawed 48 hours before roasting.
Unwrap goose and place in roasting pan. Refrigerate for 48 hours.
Preheat oven to 425. Place rack in lower third of oven.
Peel, core, and quarter apples. Set aside.
Plump prunes in warm water for about 30 minutes. Drain, cut in half, and mix with apples.
Remove neck and giblets from large cavity in goose. (Set aside for gravy, if desired.)
Remove excess fat and set aside. (See description above for how to render fat.)
Check carefully for any remaining small feathers. Pluck or singe any you find.
Rinse goose, inside and out, with cold water. Dry thoroughly with paper towels.
Salt goose, inside and out.
Stuff large cavity with apple and prune mixture.
Pull tail over cavity opening and close with small skewers.
Place goose on rack, breast facing up, and set in roasting pan.
Roast at 425 for 30 minutes.
While goose is roasting, melt butter in small saucepan with 1 to 2 cups hot water. Set out a baking sheet (with sides) large enough to hold roasting rack, and a medium bowl (not plastic).
Remove roasting pan from oven and place rack and goose on baking sheet. Carefully pour excess fat from roasting pan into bowl.
Lower heat to 350.
Put rack and goose in roasting pan. Carefully flip goose so that its back is facing up. Baste goose with butter and water, and then sprinkle with a bit of the flour. (This will help the skin brown and also absorb some of the fat.)
Put goose back in oven.
After every 30 minutes, take the goose out and repeat the process (drain - flip - baste - flour). For the final 15 minutes of roasting, the goose should be breast up.
After goose has roasted for 2 to 2-1/2 hours, check the legs to see how loose they are. The goose is done when the legs are really loose.
Remove goose from pan and rack and set on cutting board, breast up. Let rest for 15-20 minutes before carving.
Tip on carving: do your best, and do it in the kitchen. Be sure to show the goose off to your guests before carving!