Cut the baguette into 1/2-inch or so slices, but don’t cut all the way though the bread; the goal is for the slices to remain attached at the bottom. See above for details about using chopsticks along the sides of the bread to prevent slicing all the way down.
Use a brush to smear the pesto in between the slices, making sure to brush some of the pesto on both sides of each slice. Place the baguette on a large piece of foil, and pull the foil up around the sides of the bread, but not over the top – you want the top to be able to brown.
Bake for about 20 minutes until the bread is hot and the top is lightly browned and crusty. Serve hot.