Preheat oven to 350°F (180°C). Line a baking sheet with parchment paper and cooking spray.
Arrange bread cubes on the prepared baking sheet, ensuring there is a little space between each cube.
Put the baking sheet in preheated oven. Toast the bread cubes for 15-20 minutes, turning the cubes after 10 minutes. Heat until toasted and crunchy. Remove from oven and leave to cool.
Heat canola oil in a frying pan or skillet over medium heat. Add the celery and onion. Sauté until celery and onion are translucent.
Add sage, thyme, and garlic to skillet. Cook for a further 2 minutes.
Transfer mixture to a large bowl. Add toasted bread, salt and black pepper, and combine thoroughly.
Slowly stir in vegetable broth, allowing for even coverage.
Once combined, transfer the mixture to a baking dish. Bake in oven at 375°F (190°C) for 30 minutes, or until golden brown and crunchy.
Remove from oven and serve immediately while warm.