Preheat the oven to 275 degrees. Line a baking sheet with tin foil then coat it with cooking spray.
Core the tomatoes. Slice the larger tomatoes in half and leave the small ones whole. Place on the baking sheet, cut side up. Slide the slivers of garlic into the tomato halves. Season with black pepper, dried basil, dried oregano, to taste. Drizzle the top of the tomatoes with a bit of olive oil.
Place into the oven and roast for 90 minutes then turn the tray. Return to the oven and continue to roast for 90-120 minutes, or until juicy and roasted. Place on the counter to cool then season with sea salt, to taste. Once they are cool, put the tomatoes and their juices into a storage bowl with a lid and place them into the refrigerator until needed.