Preheat the oven to 400°F.
Remove one large or two small garlic cloves from one of the bulbs and set them aside.
Cut the tops off of your garlic bulbs, then arrange each on a sheet of foil. Drizzle each with a tablespoon of olive oil, then loosely enclose the bulbs in the foil. (Note 1)
Roast the garlic until the cloves are soft and browned, about 30 to 40 minutes.
Remove the garlic from the oven, loosen the foil, and allow the bulbs to cool for a few minutes. Leave the oven on.
When the garlic is cool enough to handle, squeeze the bulbs to extract the roasted garlic. It will be super soft. Place the roasted garlic into the bowl of a mini food processor (Note 2), along with the basil, the reserved raw garlic clove(s), the remaining ½ cup of olive oil, and salt.
Blend the mixture until smooth. Taste-test the mixture and season it with red pepper flakes and additional salt, if desired.
Slice the loaf of bread in half, lengthwise, then slather the cut side of each loaf half with the roasted garlic mixture.
Place the loaf halves into the oven, directly on the rack, cut side up. Bake for 10 minutes or until crispy. Optionally, place the loaves under the broiler for 1 to 2 minutes at the end of baking.
Slice and serve.