Add the scallops, oil, garlic, lemon juice, salt, and pepper to a bowl and mix. Cover and place in the refrigerator and marinate for 2 to 24 hours.
Preheat the grill to 450° to 550°.
Once the grill is hot, add the scallops along with the lemon slices to the grill, cook for 3 minutes on one side, and then flip and cook for 30 seconds. This will give you a medium-rare to medium internal temperature. Serve or keep warm.
Coat the tomatoes in the 3 tablespoons of olive oil, season with salt and pepper, and add to the grill just to blister, about 1 to 2 minutes. Keep them warm.
Add the remaining 1/2 cup of olive oil, lemon juice, and chives to a blender and blend until completely smooth. Let sit for 5 minutes and then finely strain. There will be plenty of leftovers to use in other recipes.
Serve the scallops over top of the polenta, along with a drizzle of chive oil and a side of roasted tomatoes.
Make-Ahead: Scallops are meant to be eaten as soon as they are finished cooking.How to Reheat: Re-grill the scallops in the exact same method but cut the cooking times in half so as to not overcook.How to Store: Cover and keep in the refrigerator for up to 3 days. These will not freeze well, and I would recommend freezing them un-cooked.Scallops are meant to be eaten at a more medium-internal temperature.They will overcook very quickly and become very chewy.If you have the option, always buy dry-packed scallops. Wet-pack scallops are packed in cold sea water along with preservatives to extend the shelf life.Also, try serving the scallops with a simple beurre blanc.If you are nervous that the scallops will fall through the grill grates, you can use two skewers pierced through 6-8 scallops. The skewers should be about a ½” inch from each other all the way through so that the scallops are balanced and not turning when lifting them up on the skewers.