Line a baking sheet with parchment paper.
Melt butter in a saucepan over medium heat.
Add sweetener and cook 2–3 minutes until bubbly.
Stir in heavy cream, salt, and vanilla.
Simmer 2–3 minutes until caramel thickens slightly.
Add almonds and stir to coat completely.
Drop spoonfuls onto the parchment.
Sprinkle with flaky sea salt.
Chill 20–30 minutes until firm.