It's hard to describe in words, but it involves a lot of leveling, a lot of smoothing. The tongue stays closer to the center of the mouth rather than doing the pronounced, defined highs and lows that shape the L and R sounds. The vocal cords vibrate in smooth, singing tones rather than doing the little hop up and down that makes for a normal American English syllable.
And after a few practice sentences, it slips effortlessly from my mouth. "Herro, and wercome to Beijing. Zhis is yoah guide to an ancient culchah ..."
Lo and behold, I'm speaking English in a "Chinese accent."
I shouldn't complain — no actor can really get upset about a source of steady work. As I've pointed out, when Asian characters don't have accents it just means that white voice artists end up playing them. In all the kerfuffle about the "whitewashing" of M. Night Shyamalan's live-action version of The Last Airbender, people totally ignored that the voice cast of the cartoon it was based on was also almost all white people playing Asian characters.
