- To make ahead, prepare crostini as directed above except do not bake. Layer crostini between sheets of waxed paper in a resealable plastic freezer container; freeze. At serving time, heat oven to 350°F. Place desired number of crostini onto ungreased baking sheet. Bake 12-15 minutes or until cheeses are melted. Serve warm; garnish with sprig of fresh herb, if desired.