To toast pecans in the oven:

Preheat oven to 350 degrees. Line a rimmed baking sheet with parchment paper or foil for easy cleanup.

Toss pecans in oil or melted butter and salt if desired. Arrange in a single layer on the prepared baking sheet. Toast until browned and fragrant, stirring occasionally, about 5 to 10 minutes. 

Remove from oven and chop or use as desired. Or, store in an airtight container for up to 1 week. Or freeze for longer.