All tiles are unwalkable.
Dungeon DMap (doesn't even matter if the offset is wrong, as long as link doesn't have to walk around on any normal screens in the DMap).
Link placed at either the left or right side of the screen, at or below the middle (keeping in mind that when Link's above the middle, the person talking makes him stuck).
Alternate between left and right for each screen, and use sidewarps to switch from one screen to the next.