You would resolve any leaning or stacked kubbs before the rest of the group. The rules says this is how you resolve those kubbs that are stacked:
"6. Any field kubb that, after having been thrown, comes to rest horizontally on top of one or more other field kubbs is to be lowered directly to the pitch, touching the lower kubb. Note: Defender chooses what side to lower if both ends are unobstructed and in-bounds
(a) If this is impossible on one end due to obstruction or the boundary of the pitch then it must be done on the unobstructed and in bounds end. The bottom kubb cannot be moved until the elevated kubb is resolved.
(b) If this is impossible on either end due to obstructions then un-raised kubbs must be resolved in a legal manner that allows the elevated kubb to be lowered directly to the pitch. "