Coarsely chop the remaining 12 oz of chocolate, reserve 1/4 of it and finely chop that portion. Transfer the coarsely chopped portion to a microwave-safe bowl.
Heat the chocolate on full power for 30 seconds and stir. Heat another 30 seconds and stir again, scraping the sides and bottom of the bowl with a rubber spatula.
Continue heating the chocolate in bursts of 5-10 seconds, stirring vigorously after each one, until the chocolate is 70% melted. Stir until the chocolate is fully melted from the residual heat.
Once the chocolate is fully melted and smooth, add half the FINELY chopped chocolate and stir until fully melted.
Add half of the remaining finely chopped chocolate, and stir again until fully melted. Keep adding chocolate, 1 or 2 tablespoons at a time and stirring until melted.
When it starts to take a few minutes of stirring before the added chocolate fully melts, test the temper by dipping the back of a metal spoon into the chocolate and setting it down on the counter. It should start to set after about 5-8 minutes. Keep stirring while you wait. If it has not set, add a little more chocolate, stir until melted and try again. Your chocolate is tempered when it sets with a beautiful shine and no streaks.
Using a dipping fork, or a regular fork, dip each truffle, rolling it around to cover completely, tap the for against the side of the bowl to remove excess chocolate, and put on the prepared baking sheet. Sprinkle with a little flaky sea salt before the chocolate sets.