Heat oven to 350°F. Line a 9x13-inch pan with parchment, leaving overhang. Lightly grease.
Whisk flour, oats, brown sugar, baking soda, and fine salt in a large bowl.
Stir in melted butter until the mixture looks damp and clumpy.
Press about two-thirds of the mixture firmly into the pan. Reserve the rest for topping.
Bake the crust for 10–12 minutes until set and lightly golden at the edges.
Melt caramels with heavy cream in a saucepan over low heat, stirring until smooth. Remove from heat and stir in vanilla.
Scatter chocolate chips over the warm crust. Pour the warm caramel over and spread gently.
Crumble the remaining oat mixture over the caramel, leaving some caramel peeking through.
Bake 18–20 minutes until the top is golden and the caramel bubbles at the edges.
Cool completely in the pan. Chill 30–45 minutes for cleaner cuts, then lift out and slice into bars. Finish with flaky sea salt.