Preheat oven to 250 degrees and grease a large baking sheet.
Combine sugar, salt, and cinnamon in a small bowl. Set aside.
In a large bowl, whip the egg white and vanilla until it gets frothy, about 1 minute.
Add almonds to the egg mixture and stir until they're evenly coated.
Pour the dry mixture over the almonds and mix together until they're evenly coated.
Spread the almonds into an even layer on the baking sheet. Bake for 1 hour, stirring every 15 minutes.
Remove the almonds, stir once more, then allow to cool.
Store in an airtight container for up to 2 weeks, or in the freeze for up to 3 months.