How to report after the end game screen.

I recently played a ranked game where from the beginning players were caustic, stubborn, refused to communicate, and threw the game after dying twice.

I wanted to report them, as they made the game frustrating and overall un-enjoyable, but I accidentally exited out of end game screen. How do you report players after the end game screen?

I've played league for several years and It seems the community is still as toxic as ever, despite Riots attempts to crack down. It's one thing to lose a game, but when players deliberately ruin the game for others it deters the desire the play ranked and the competitiveness you would expect in a ranked game.