Just place the cubes of bread in a bowl, together with the oil, and stir them around so that they get an even coating.
Then arrange them on a baking sheet. Bake them on a high shelf in the oven for 10 minutes or until they are crisp and golden. One word of warning: do use a kitchen timer for this operation because it's actually very hard to bake something for just 10 minutes without fogetting all about it. Then cool on the baking sheet and store in an airtight container.