Heat oven to 275 degrees F. Line large rimmed baking sheet with parchment paper.

In large bowl, stir oats, hazelnuts and sea salt to combine. Use wooden spoon to stir in Nutella and olive oil until well combined. Spread mixture in thin even layer on prepared baking sheet.

Bake 40 to 45 minutes, stirring halfway through, until granola is golden brown. Cool completely on baking sheet (do not stir so clumps can form!), about 1 hour to 1 hour 30 minutes.

Store granola in airtight container at room temperature up to 2 weeks.

*To toast hazelnuts, stir hazelnuts in skillet over medium high heat for about 3 to 5 minutes until hazelnuts smell toasted and start to brown. Immediately remove from heat.