Heat oven to 350°F. Line a 9-inch square pan with parchment, leaving overhang. Lightly grease.
Whisk oats, flour, baking soda, and fine salt in a large bowl.
Stir melted butter with brown sugar and vanilla until glossy and smooth.
Combine wet and dry mixtures to form a damp, crumbly dough.
Press about two-thirds of the dough into the pan. Bake 10 minutes.
Melt caramels with heavy cream in a small saucepan over low heat, stirring until smooth.
Scatter chocolate chips and pecans over the warm crust.
Pour the melted caramel evenly over the top.
Crumble remaining dough over the caramel in small clumps. Sprinkle flaky sea salt if using.
Bake 15–18 minutes more, until edges are deep golden and caramel is bubbling.
Cool completely on a rack. Chill 30 minutes for cleaner cuts, then slice into bars.