I've looked at other questions here about toddlers throwing food. But they seem to do it for the fun of watching things fall, or in the middle of their meal. So those answers do not apply to my situation.
My son only starts to throw food when he doesn't want to eat any more. This may be because he's full or he doesn't like the food. So taking food away is not "punishment" - that is what he expects from us. He doesn't even look at the food he's thrown down, so I can't imagine it's for the fun of throwing. (He did use to throw food for fun and attention a few months ago. He has mostly stopped doing that after we stopped paying him attention as soon as he starts throwing food. That tactic hasn't worked for throwing because he's done.)
We always ask him "do you want more?" before serving him again and he nods yes if he does. When he starts throwing we ask him "are you done?" and he nods yes. He can say the word "done", but just doesn't when he's done eating. He throws food instead. How can we help him communicate instead of throw?
P.S : We're mostly doing baby-led weaning (BLW), with occasional purees and mashed things that we feed him. He likes eating on his own better than being fed.