Make sure snappers are clean from the insides and scales have been removed. Pat dry with paper towel. Season with olive oil inside and outside. Add sea salt and pepper as well generously inside and outside of each fish.
Sprinkle olive oil on the baking dish and make sure the surface is well oiled so it's not sticky. Add the fish and arrange so all 3 fit. Cut slits or score each fish 2-3 cuts on the upper side. Add lemon slices on the cuts. Sprinkle lemon juice generously over, inside etc.
Bake for about 25 minutes or until fish is flaky. This depends a little on how thick the fish is. Usually the skin becomes golden with brown edges when it's ready. Broil for a minute or two if you like crispy skin. Don't broil for too long so fish doesn't dry up.
Serve on a platter with greens of your choice and a big salad. Sprinkle more lemon juice over the fish on the platter. Add plenty of lemons slices everywhere so your guests can add more lemon as they serve the fish. Enjoy fresh:)).
Word of warning - fish can have little bones, try to avoid those and help kids break their fish in small pieces to avoid eating the small bones.
Notes
Work around the big skeleton when you eat the fish and watch out for the little bones. The bigger the fish, the easier to spot and remove the small bones