Highlighted: where the king and rook start and land.
Weirdest castling #6
SP-12 · qbnnrkbr
O-O · K f1→g1 · R h1→f1
78 of the 960 starts castle exactly this way.
Destinations are fixed in Chess960 (kingside K→g1 R→f1, queenside K→c1 R→d1); only the starting squares differ.