It was Speak From the Heart, which is set during 3x17, specifically the part where Oliver does his best man speech. I mentioned to Stephen that that was one thing I felt was missing in the episode, and after he read it he said “that’s awesome” and even now I feel like jumping up and down at the very memory. :D
I was very specific that it wasn’t something dirty, though, just because I knew it was a strange request as it was and I didn’t want to make him uncomfortable. Hence the G-rated fic with speeches about love and Ollie very innocently mooning over Felicity (as opposed to, say, my latest fic where Oliver and Felicity go home together after everything that happens in 3x23 and end up having a grope on the Ducati and then sex on her kitchen counter… oops).