Preheat oven to 400 degrees.
Combine flour, sea salt, black pepper, baking powder, and baking soda in a large bowl, and whisk to combine.
Using a pastry cutter or two knives, cut your butter into the flour. Essentially, this just means work it into the flour until your butter is the size of small peas scattered throughout, and the mixture is very crumbly. Despite the fact that my Uncle wanted me to make "hand squashed biscuits" I actually try to keep my hands out of these at this stage, as I don't want my body heat to warm the butter. The colder the butter, the flakier (and puffier) the biscuits will be.
When your butter is worked in, make a well in the flour mixture and pour in the buttermilk, folding in the flour on the sides as you go. Don't overwork the flour, but fold it together until all of the buttermilk is incorporated.
Take the dough and lay it on a piece of floured parchment paper. Roll or pat the dough out til it's about 1/2 inch thick, and then fold each side in. Repeat this process twice. This process gives a kind of lamination to the dough, or in laymen's terms, it helps it rise.
Spread the dough out to about half inch thick again, and using a biscuit cutter or a mason jar, cut out biscuits without twisting the biscuit cutter or mason jar. You don't want to finish the edges by twisting the cutter, as that will impede the biscuit's rise.
Place biscuits on a cookie sheet so that all the biscuits are touching, and brush the tops with a little leftover buttermilk or even melted butter, for a more golden appearance.
Using your finishing salt, place a few flakes on top of each biscuit.
Bake for 12-15 minutes, or until the tops are browned and the biscuits are cooked through.