First, heat 1 cup of water until it is warm to the touch or it reaches 110°F. Stir in the coconut sugar and the yeast. Set it aside and let it activate for 10 minutes.
In the bowl of a stand mixer, pour in the flour and salt and stir. Add in the softened butter and yeast mixture. Use the dough hook attachment to combine the ingredients together on medium-low speed, scraping the sides as needed. Mix until combined and until the dough becomes sticky. (If you don't have a stand mixer, just use a mixing bowl and spoon)
Then cover the bowl with a towel or plastic wrap. Set it in a warm place for an hour for the dough to proof.
Toward the last 15 minutes of the dough rising, pour water and stir in baking soda in a large pot and place it over the stove on medium--high heat. Preheat the oven to 450°F and set out a non-stick baking sheet or one with a silicone mat that can withstand high heat.
Then lightly flour the counter or flour a sheet of parchment paper placed on the counter. Lightly flour your hands and place the dough onto the flour. Divide the dough in half and then divide each half into 4 clumps, for a total of 8. Roll each clump into a round and gently press down on the tops.
Once the soda bath is boiling, use a stainless steel strainer to lower one roll at a time into the bath. Make sure the whole roll gets coated with water and allow the roll to float in the water above the strainer for 20 seconds. Lift the roll out of the bath, allowing excess water to drip off. Flip it gently upside down onto the baking sheet. Repeat until just enough rolls fit on the baking sheet spaced a couple inches apart.
Reduce the baking soda bath temperature to low until you are ready to bathe and bake the remaining rolls. Sprinkle the tops with coarse sea salt and bake on the middle oven rack for 15 minutes. Allow the rolls to cool for 5 minutes before using a spatula to transfer them to a cooling rack.
Bring the baking soda bath to a boil once again and repeat the steps until all rolls are cooked.