If you have an American Express Platinum charge card, you can book with Platinum Travel Services (PTS) by phone. Some countries may have an online booking option, but that typically only gives you the cheapest fare ("R" / "P" class where lounge access/seat selection is not available).
I just give the PTS agent segment by segment the flights I want. When booking QR, I tell them I want "I" class (and not to book "P" or "R" class) or so that I get both lounge access and seat selection.
In Canada, PTS does not charge a ticketing fee and they are available 24 hours a day.