I used to be the same way.
I did a lot of things.
First- I figured out how long it took me to eat (I found it was within 5 minutes! No wonder I'd overeat!)
Then I decided to double that. 10 minutes. I started drinking a sip of water between each bite. I put down my fork, I did NOT hold my fork or eat while talking. I mean literally I was looking at the clock the whole time (I know it sounds crazy) to make sure I wasn't going too fast.
Then when I could do 10 minutes I switched up to 15, then 20 minutes. At 20 I felt that I was at a good enough pace
It was tough but I remember it took me a few weeks to really get it down to where it was more natural.
Now I'm usually the last to be done! It sort of backfired on me