Line a 9 x 13 pan with foil or parchment paper. Grease parchment paper.
Set aside 2 Tbsp of butter and put the rest in a bowl. Beat butter until smooth.
Add in brown sugar and baking soda. Beat until combined
Beat in eggs and vanilla. Add in flour and beat until combined.
Beat in oats.
Salted Caramel Filling
In a medium pan combine remaining 2 Tbsp butter, the caramels and sweetened condensed milk. Cook over low heat, stirring until melted and smooth.
Remove from heat and add in 1 tsp sea salt.
Press 2/3 of mixture oat mixture into the bottom of prepared baking pan. Spread caramel mixture over the top and crumble the remaining oat mixture over the top of the caramel mixture. Sprinkle with remaining salt.
Bake for 20-25 minutes. It will still look a little "wet" but will set up as it cools. Cool in pan on wire rack. Using the parchment paper, lift the bars out of the pan and cut to serve.