For the crust, place the butter, flour, 1/2 cup brown sugar and half the salt in a food processor.
Pulse a few times until the mixture is crumbly and well combined.
In a large mixing bowl, whisk together corn syrup, remaining 1/4 cup brown sugar, eggs and pecans, with remaining sea salt.
Line the slow cooker with baking paper (just so the pie will remove easily).
Press the crumbly dough into the bottom of the slow cooker and slightly up the sides.
Pour the pecan mixture over the crust.
Lay a tea towel between the slow cooker and the lid to absorb condensation.
Cover and cook on HIGH for 3 hours.
Cool completely before slicing to serve.