Position a rack in the middle of the oven and preheat the oven to 375°F (190°C). Line a baking sheet with parchment.
In a large mixing bowl, whisk together both flours, the fine sea salt, baking powder, sugar, and baking soda.
Add the cold butter cubes and toss to coat. Working quickly, cut in the butter with a pastry blender, or pinch the cubes with your fingertips, smearing them into the flour.
Make a well in the center of the dry ingredients, pour in the buttermilk, and use your hands to mix the dry ingredients into the buttermilk until you have a shaggy dough.
Gently turn the dough out onto a clean work surface. Using the heel of your hand, smear the butter into the flour.
Bring the dough together by smearing, folding, and turning it, then repeat until there are no more dry bits of flour remaining.
Flour a rolling pin and lightly dust your work surface with flour. Roll the dough into a 12-by-14-inch (30 by 36 cm) rectangle.
Begin by doing a tri-fold, starting from the right: Fold the right side of the dough over the center and then fold the left side over the first fold.
Rotate the dough 90 degrees and roll it out again into a rectangle, then fold the dough in half from the top down.
Roll the dough out again into a rectangle and fold it in half once more.
Using a bench scraper or a sharp knife, cut the dough in half and stack the bottom half on the top half.
Dust the dough lightly with flour, and roll the dough out again into a rectangle about 1 inch (3 cm) thick.
Dip the edges of a 2¼-inch (6 cm) biscuit cutter in flour and punch out the biscuits; do not twist the cutter.
Arrange the biscuits 1 inch (3 cm) apart on the prepared baking sheet.
Gather up your scraps, press them together until you have a cohesive mass, roll them out again, and cut more biscuits.
Brush the tops of the biscuits with the melted butter and give each one a sprinkle of flaky sea salt.
Bake for 25 to 30 minutes, until golden brown.
Source: eu.savannahnow.com/story/entertainment/2021/12/28/how-to-make-perfect-southern-biscuit-back-in-the-day-bakery-savannah-ga/8975607002/
