Advice for slow eaters?

My 7 year old takes forever to eat, even when it's food he genuinely likes!!! I've tried distractions/ no distractions and trying to remind him to continue to eat. We start off eating together but everyone else will be done at most after 45 minutes and he will still be sitting there for another hour+ eating a bite here and there. I've also tried smaller meals throughout the day but the size doesn't seem to matter!

I don't want to take his food away or cause him any food related problems and am not sure if timer setting is a viable or healthy option? Any suggestions would be welcome!

Also he does go to school and tells me he has no problem eating the school lunch before the period ends so I'm really not sure what the problem is. This has been for going on 2 years now!